Treated versus self-reported prevalence of chronic pain and costs of patients’ health services utilization: a population-based study of health administrative databases

Abstract

Objectives

To compare treated to self-reported prevalence of chronic pain (CP) and to estimate health services utilization (HSU) costs of patients treated for CP in Alberta, Canada.

Methods

Patients treated for CP were identified by the physician billing codes of health services for CP from the practitioner claims database in fiscal year 2021/22. The treated prevalence of CP (number of these patients divided by the population) was compared to the self-reported prevalence of CP previously estimated (doi:10.1371/journal.pone.0272638). Costs of patients’ HSU included costs for general practitioner (GP), specialist, inpatient, emergency department, outpatient clinic services, and prescription drugs.

Results

The treated prevalence of CP was 6.0% (4.4% among males and 7.8% among females) which was 30% to 41% of the self-reported prevalence. The highest treated prevalence (7.2%) was found in the age group of 18–64 years, followed by age groups of >64 years (7.0%) and <18 years (2.1%). The average cost per patient per year was $5096 ($5878 for males and $4652 for females), of which hospitalizations accounted for 65.0%, outpatient clinic visits 16.4%, ED visits 9.5%, prescription drugs 4.7%, GP visits 3.9%, and specialist visits 0.4%. The total cost of patients with CP for the health system was $1.37 billion (∼7% of total health expenditure), of which males accounted for 41.7% and females for 58.3%.

Discussion

Our findings suggest that the economic burden of CP is considerable and that many people with self-reported CP do not use the public healthcare services. This can be multifactorial, including lack of availability and accessibility of publicly funded services, people’s lack of awareness of available services, lower utilization due to COVID-19 pandemic, and reliance on self-management, private services, and alternative treatments. Further studies are warranted to inform future policies and health system initiatives aiming to reduce the burden of CP and improve lives of people living with it.

Introduction

Chronic pain (CP) refers to pain being persistent for 3 months or more. ¹ CP is one of the leading causes of disability and morbidity in Canada and globally. ² It is estimated that 19 to 22% of Canadians aged 18 or older experience CP.^3,4 In Alberta, Canada, we have recently estimated that the prevalence of any CP is 20.1% and of activity-preventing CP is 14.5% among people aged >=12 years. The health services utilization (HSU) cost per person with CP per year has been estimated at CA$2217 and for the whole province of Alberta it is estimated from CA$1.2 to CA$1.7 billion equivalent to 6% to 8% of total provincial health expenditure. Of the HSU cost, inpatient services account for 31%, outpatient services for 13%, physician services for 10%, prescription drugs for 33%, and other services for 13%. ⁵

Although the study was comprehensive and its’ results were comparable with estimates in other studies and jurisdictions (such as Ontario), ⁶ there are several limitations which this paper attempts to address. For example, the International Classification of Diseases (ICD) 9 or 10 codes for CP (338.^ or G89.^) have not been used in the Alberta Health administrative databases; thus, the HSU costs of CP cannot be estimated directly, but through CP-related conditions and the weights – percentages of CP due to these conditions, which are adapted from Australia. ⁷ In addition, the prevalence of CP is subjective and not specific to pain lasting >=3 months as it is based on the Canadian Community Health Survey data. ⁸

While the ICD chronic pain codes have not been implemented in Alberta, the Alberta Health Care Insurance Plan Practitioner Claims Database that includes information on claims submitted by physicians and other allied practitioners could provide an opportunity as a majority of pain-related cases in administrative data tend to come from physician visits. ⁹ Furthermore, the Alberta Health Care Insurance Plan covers the entire Alberta population since health care is publicly funded and the Practitioner Claims Database contains billing codes (as shown in the Medical Price List) ¹⁰ of health services for CP. ¹¹ Health coverage includes all physician visits, medical interventions and hospitalizations. Coverage of chiropractic, physiotherapy, psychology treatments and other allied health therapies is not usually publicly funded.

In this article, we report results of an analysis regarding the prevalence of physician-treated CP (hereafter called treated prevalence of CP) by age and sex groups and costs of health services used by these patients using the Alberta Health Administrative Databases, given the effectiveness of using healthcare administrative data to track service utilization, monitor costs, and assess quality. ¹²

Methods

Data sources

The Alberta Health Administrative databases, which are linkable by the patient’s unique lifetime identifier, ¹³ were used to identify patients with CP and their HSU in this study, including the Practitioner Claims Database, Discharge Abstract Database, National Ambulatory Care Reporting System, and Pharmaceutical Information Network. The Practitioner Claims Database consists of claims to pay medical doctors and other allied practitioners. Data elements include patient information (such as identifier, demographic information, location), provider information (such as identifier, speciality, role, location, referring provider identifier and discipline), and service information (such as billing code of health services, date of service, amount paid, diagnostic codes, and shadow billed claims). The Discharge Abstract Database contains information about acute inpatient care, including treatment, examination, and observation for patients occupying a hospital inpatient bed. Data elements include demographics, admission/discharge/transfer information, provider information, diagnoses, intervention, special care unit information, and Canadian Institute for Health Information’s Case-Mix Group Plus derived data. The National Ambulatory Care Reporting System includes information about ambulatory care that is provided in a publicly funded clinic, day surgery, and emergency department settings. In the Pharmaceutical Information Network, a record is created each time a prescription is dispensed to a patient. Data elements include drug dispense event information (dispense date, pick-up date, cancelation date); patient, prescriber, dispenser, and facility information; drug information details, such as drug identification number, anatomic therapeutic classification code, quantity, and compound components.

Study design and patient identification

We applied a retrospective cross-sectional design studying the above-mentioned administrative databases in fiscal year 2021/22 (from April 1, 2021 to March 31, 2022) extracted by July 6^th, 2022. Claims for health services relating to CP were identified from the Practitioner Claims Database by the billing codes which were verified by physicians (LSM and MR) being shown in Table 1. These codes covered both cancer and non-cancer CP and were searchable from the Fee Navigator of the Alberta Medical Association website (https://www.albertadoctors.org/fee-navigator) or from the Medical Price List of the Alberta Health Care Insurance Plan website (https://open.alberta.ca/publications/somb-2022-02-01). ¹⁰ Patients who had at least one of these claims were considered patients with CP and were included in analyses. We linked the patients’ unique lifetime identifier to the Discharge Abstract Database, National Ambulatory Care Reporting System, and Pharmaceutical Information Network databases to retrieve their utilization of inpatient services, outpatient services, and prescription drugs, for any reasons or diagnoses in the same fiscal year, respectively.

Table 1.

Billing codes of health service relating to chronic pain.

Code	Description
03.08F	Formal, comprehensive consultation, for a patient with chronic pain, full 60 minutes or major portion thereof for the first call when only one call is claimed
03.05O	Direct management, reassessment, education, and/or general counselling of a patient with chronic pain, per 15 minutes or portion thereof
03.05LB	Group teaching session for patients and/or family members with chronic pain, previous amputation, stroke, brain injury, concussion, spinal cord injury, or other neuromusculoskeletal condition, first 45 minutes or major portion thereof for the first call when only one call is claimed
03.05X	Formal, scheduled, professional interview with relative(s) relating to the care and treatment of a patient with chronic pain on behalf of a specific patient, full 15 minutes or major portion thereof for the first call when only one call is claimed
03.05V	Formal, scheduled, professional interview relating to the care and treatment of a patient with chronic pain with other physicians, and/or direct therapeutic supervision of allied health professionals or community agencies, on behalf of a specific patient, per 15 minutes
03.05W	Second and subsequent physician attendance at a formal, scheduled, professional interview relating to the care and treatment of a patient with chronic pain with other physicians, family, and/or direct therapeutic supervision of allied health professionals or community agencies, on behalf of a specific patient, per 15 minutes
03.05JM	Formal, scheduled, professional conference related to the care and treatment of multiple patients undergoing rehabilitation therapy including those with chronic pain with other physician(s), allied health professionals, educational, correctional, and other community agencies on behalf of a specific patient provided by the physiatrist most responsible for the patient’s care per full 5 minutes to a maximum of 6 units in a 30-minute period
03.05JN	Second and subsequent physician attendance at a formal, scheduled, professional conference related to the care and treatment of multiple patients undergoing rehabilitation therapy including those with chronic pain, when discussion occurs on behalf of a specific patient per full 5 minutes to a maximum of 6 units in a 30-minute period
08.19CW	Telephone or secure videoconference with a patient for scheduled psychiatric treatment (including group therapy) by a general practitioner or pediatrician, or for a palliative care or a chronic pain visit by an eligible physician, per full 15 minutes.

Sources: https://www.albertadoctors.org/fee-navigator/hsc/search/chronic/pain and https://open.alberta.ca/publications/somb-2022-02-01 (accessed July 22, 2022).

Costing methods

Costs for inpatient and outpatient services were based on the Canadian Institute for Health Information Case-Mix Group plus and Comprehensive Ambulatory Classification System methodology, which included both medical and non-medical (e.g. support and administrative departments, such as information systems, housekeeping, and finance) costs.^14,15 The cost for each Case-Mix Group plus and Comprehensive Ambulatory Classification System group was retrieved from the Alberta Health Interactive Health Data Application. ¹⁶ The cost for physician services was defined as paid amounts available in claims that physicians made to the Alberta Health Care Insurance Plan. For the alternative relationship plan (e.g. physicians are on salary) claims (∼10%) where the paid amounts were not available, we used the ‘system assessed amounts’ as a proxy. Costs for prescription drugs were based on prices per unit by drug identification number listed in the Alberta Drug Benefit List. ¹⁷

Statistical methods

The treated prevalence was defined as the number of patients treated for CP by physicians being divided by the population. To compare to the self-reported prevalence of CP, we calculated the treated prevalence as a percentage of the self-reported one that we estimated previously using the Canadian Community Health Survey data. ⁵ Patients’ HSU cost components included costs for inpatient, outpatient (emergency department [ED] and clinic), and physician (general practitioner [GP] and specialist) services, as well as costs for prescription drugs dispensed from community pharmacies. We estimated average costs per patient and total costs for the whole province. Furthermore, we estimated the number and percentage of users of other health services (hospitalizations, ED and outpatient clinic visits, and prescription drugs) among patients treated for CP by physicians. We also estimated average costs per patient among these users. All the outcomes (utilization and costs) were analyzed by health service (inpatient, emergency, outpatient clinic, specialist, general practitioner, and prescription drug), and by patients’ characteristics, including sex (male and female) and age (<18 years, 18 to 64 years, and >64 years) groups. Of note, we included any hospitalizations, any outpatient visits, and any prescription drugs in fiscal year 2021/22 that were linked to the unique lifetime identifier of patients being treated for CP by physicians identified from the Practitioner Claims Database in calculations mentioned above. In Appendices, we reported frequencies and percentages of the diagnosis responsible for patients’ utilization of inpatient and outpatient services (approximately 80% of these diagnoses were those commonly comorbid with chronic pain, including mental health-related diagnoses). Also, we separated opioids from other prescription drugs using the anatomic therapeutic classification codes. ¹⁸

Stata SE 17.0 (www.stata.com) was used for analyses. All costs were converted to 2022 Canadian dollars using the Bank of Canada Inflation Calculator. ¹⁹

As this study was a secondary analysis of previously collected data by Statistics Canada and Alberta Health, the Research Ethics Board at the University of Alberta indicated that obtaining additional informed consent was not required. It was ethically approved by the Research Ethics Board (File # Pro00110848) on May 25, 2021.

Results

In fiscal year 2021/22, there were 268,672 unique patients (97,198 males and 171,474 females) being treated for CP by physicians (Table 2). The top diagnoses for these physician visits were Mental Disorders 65.8%, Diseases of the Musculoskeletal System and Connective Tissue 11.7%, Infectious and Parasitic Diseases 5.3%, Symptoms, Signs and Ill-defined Conditions 5.2%, Injury and Poisoning 4.0% (for more see Supplementary Table S1). Given the 2021/22 Alberta population was 4,442,679 (2,232,197 males and 2,210,482 females), ²⁰ the treated prevalence of CP was estimated at 6.0% (4.4% in males and 7.8% in females). The highest prevalence was found in the age group of >64 years old among males (5.5%) and in the age group of 18–64 years old among females (9.5%). The lowest prevalence was found in the youngest age group (<18 years), both among males (1.9%) and among females (2.3%). Compared to the self-reported prevalence, ⁵ the treated prevalence was considerably lower. For example, for all age and sex groups, the treated prevalence of CP was proximately 30% of the self-reported prevalence of any CP (6.0% vs 20.1%) and 42% of the self-reported prevalence of activity-preventing CP (6.0% vs 14.5%). The ratio between treated and self-reported prevalence varied by age and sex groups. Specifically, the ratio was lower in males compared to females for both any CP and activity-preventing CP. Regarding age, the younger the patient the higher the ratio for activity-preventing CP. For any CP, in females and in both sexes groups, the highest ratio was found in the age group of 18–64 years.

Table 2.

Number of patients, population, and treated prevalence of chronic pain in Alberta fiscal year 2021/22 by sex and age groups.

Sex/age group	Number of patients treated for CP	Population a	Treated prevalence of CP (%)	Self-reported prevalence b		Treated prevalence as a percentage of self-reported prevalence
				Any CP (%)	Activity-preventing CP (%)	Any CP (%)	Activity-preventing CP (%)
Male
<18 years	9,509	497,382	1.9	6.7	3.4	28.4	56.9
18–64 years	71,364	1,436,261	5.0	18.6	12.5	26.7	39.8
>64 years	16,325	298,554	5.5	25.9	17.3	21.1	31.7
All ages	97,198	2,232,197	4.4	18.4	12.3	23.6	35.5
Female
<18 years	10,738	476,495	2.3	9.9	4.0	22.9	56.9
18–64 years	132,391	1,393,611	9.5	21.2	16.7	44.9	57.1
>64 years	28,345	340,376	8.3	33.0	24.4	25.3	34.1
All ages	171,474	2,210,482	7.8	21.9	16.7	35.4	46.4
Both male and female
<18 years	20,247	973,877	2.1	8.3	3.7	25.2	57.0
18–64 years	203,755	2,829,872	7.2	19.8	14.5	36.3	49.6
>64 years	44,670	638,930	7.0	29.7	21.1	23.6	33.1
All ages	268,672	4,442,679	6.0	20.14	14.46	30.0	41.8

Note. Information on p-values for any comparisons between groups is available upon request.

^afrom Statistics Canada ¹⁹ ;

^bfrom Thanh et al. 2022. ⁵

Table 3 shows the number of HSU per patient by health service and sex and age groups. On average in all sex and age groups, a patient made 2.21 visits to GP and 0.29 visits to specialists for CP per year. Compared to females, males had a higher frequency of specialist visits per patient (0.32 vs 0.28) but lower frequency of GP visits (2.04 vs 2.30). Regarding age groups, the younger the patient the higher the number of specialist visits regardless of sex groups. The highest number of GP visits was found in the oldest age group among females, and in the age group of 18–64 years among males.

Table 3.

Average numbers and costs (CA$) of health services utilization per patient treated for chronic pain by physician in Alberta fiscal year 2021/22 by health service and sex and age groups.

Sex/age group		Inpatient services	Emergency visits	Outpatient clinic visits	Specialist visits	General practitioner visits	Prescription drugs	Total
Male
<18 years	#HSU	0.12	0.65	2.74	0.63	1.10	8.28
	Cost	$2,275.89	$315.55	$929.26	$57.16	$92.58	$89.52	$3,759.97
16–64 years	#HSU	0.15	0.82	1.73	0.25	2.18	31.38
	Cost	$2,948.98	$465.83	$679.63	$17.13	$195.32	$257.58	$4,564.47
>64 years	#HSU	0.47	1.10	3.27	0.44	2.00	49.88
	Cost	$10,129.21	$781.63	$1,453.37	$30.27	$190.86	$265.76	$12,851.09
All ages	#HSU	0.20	0.85	2.09	0.32	2.04	32.23
	Cost	$4,089.10	$504.17	$834.00	$23.25	$184.52	$242.51	$5,877.55
Female
<18 years	#HSU	0.15	0.87	3.84	0.47	1.36	9.04
	Cost	$2,672.82	$465.76	$1,176.24	$39.46	$114.67	$77.66	$4,546.61
16–64 years	#HSU	0.14	0.83	1.87	0.23	2.33	27.18
	Cost	$1,966.28	$437.99	$736.96	$20.33	$214.00	$249.96	$3,625.53
>64 years	#HSU	0.35	0.92	2.65	0.46	2.51	48.04
	Cost	$7,199.25	$627.82	$1,168.51	$24.39	$207.93	$261.25	$9,489.16
All ages	#HSU	0.17	0.84	2.13	0.28	2.30	29.49
	Cost	$2,875.55	$471.11	$835.80	$22.20	$206.78	$241.04	$4,652.48
Both male and female
<18 years	#HSU	0.14	0.76	3.32	0.54	1.24	8.68
	Cost	$2,486.40	$395.21	$1,060.25	$47.77	$104.30	$83.23	$4,177.16
16–64 years	#HSU	0.14	0.83	1.82	0.24	2.28	28.65
	Cost	$2,310.47	$447.74	$716.88	$19.21	$207.46	$252.63	$3,954.39
>64 years	#HSU	0.39	0.98	2.88	0.45	2.32	48.71
	Cost	$8,270.03	$684.03	$1,272.61	$26.54	$201.69	$262.90	$10,717.80
All ages	#HSU	0.18	0.85	2.11	0.29	2.21	30.48
	Cost	$3,314.58	$483.07	$835.15	$22.58	$198.73	$241.57	$5,095.68

Note. Information on p-values for any comparisons between groups is available upon request; #HSU = number of health services utilization.

The average number of hospitalizations per patient per year was 0.18 in all sex and age groups, which was higher in males (0.20) compared to females (0.17) (Table 3). The highest number was found in the oldest age group regardless sex groups. A similar pattern was found in the numbers of ED visits and drug prescriptions with 0.85 ED visits and 30.48 prescriptions per patient per year in all sex and age groups, 0.85 ED visits and 32.23 prescriptions in males compared to 0.84 ED visits and 29.49 prescriptions in females. Also, the oldest (>64 years) had the highest numbers of ED visits and prescriptions regardless of sexes.

For outpatient clinic visits (all age group), the higher number of visits per patient per year was found in females (2.13) compared to males (2.09). The highest numbers were found in the male oldest age group (3.27) and in the female youngest age group (3.84). For both sex groups, the highest number of outpatient clinic visits was found in the age group of <18 years (3.32), followed by the age group of >64 years (2.88) and then the age group of 18–64 years (1.82).

With these HSU numbers, the average cost per patient per year, regardless sex and age groups, was estimated at CA$5095.68 (Table 3). Of this cost, hospitalizations accounted for the largest share (65.0% or CA$3314.58), followed by outpatient clinic visits (16.4% or CA$835.15), ED visits (9.5% or CA$483.07), prescription drugs (4.7% or CA$241.57), GP visits (3.9% or CA$198.73) and specialist visits (0.4% or CA$22.58). The average cost was higher in males (CA$5877.55) than that in females (CA$4652.48). However, the pattern of cost components was similar: hospitalizations accounted for the largest share (69.6% or CA$4089.10 in males and 61.8% or CA$2875.55 in females), followed by outpatient clinic visits (14,2% or CA$834.00 in males and 18% or CA$835.80 in females), ED visits (8.6% or CA$504.17 in males and 10.1% or CA$471.11 in females), prescription drugs (4.1% or CA$242.51 in males and 5.2% or CA$241.04 in females), GP visits (3.1% or CA$184.52 in males and 4.4% or CA$206.78 in females), and specialist visits (0.4% or CA$23.25 in males and 0.5% or CA$22.20 in females). Regarding age groups, the highest average cost per patient was found in the oldest age group of >64 years, which was CA$10,717.80 in both sex groups, CA$12,851.09 in males and CA$9489.16 in females (Table 3). The second highest average cost was in the youngest age group of <18 years in both sex group (CA$4177.16) and in females (CA$4546.61) but in the age group of 18–64 years in males (CA$4564.47).

Multiplying the number of patients (Table 2) with corresponding average costs per patient by sex and age groups (Table 3), the total costs of HSU of patients with CP by sex and age groups were estimated and shown in Table 4. The total HSU cost of patients with CP for the provincial healthcare system was estimated at CA$1.37 billion per year, of which males accounted for 41.7% (CA$571.29 million) and females for 58.3% (CA$797.78 million). Patients aged 18 to 64 years accounted for the largest share (57.0% or CA$325.75 million in males, 60.2% or CA$479.99 million in females, and 58.9% or CA$805.73 million for both), followed by patients aged >64 years (36.7% or CA$209.79 million in males, 33.7% or CA$268.97 million in females, and 35.0% or CA$478.76 million for both), and patients aged <18 years (6.3% or CA$35.75 million in males, 6.1% or CA$48.82 million in females, and 6.2% or CA$84.67 million for both).

Table 4.

Total costs (CA$ million) of patients treated for chronic pain by physician in Alberta fiscal year 2021/22 by health service and sex and age groups.

Sex/age group	Inpatient services	Emergency visits	Outpatient clinic visits	Specialist visits	General practitioner visits	Prescription drugs	Total
Male
<18 years	$ 21.64	$ 3.00	$ 8.84	$ 0.54	$ 0.88	$ 0.85	$ 35.75
16–64 years	$ 210.45	$ 33.24	$ 48.50	$ 1.22	$ 13.94	$ 18.38	$ 325.74
>64 years	$ 165.36	$ 12.76	$ 23.73	$ 0.49	$ 3.12	$ 4.34	$ 209.79
All ages	$ 397.45	$ 49.00	$ 81.06	$ 2.26	$ 17.93	$ 23.57	$ 571.29
Female
<18 years	$ 28.70	$ 5.00	$ 12.63	$ 0.42	$ 1.23	$ 0.83	$ 48.82
16–64 years	$ 260.32	$ 57.99	$ 97.57	$ 2.69	$ 28.33	$ 33.09	$ 479.99
>64 years	$ 204.06	$ 17.80	$ 33.12	$ 0.69	$ 5.89	$ 7.41	$ 268.97
All ages	$ 493.08	$ 80.78	$ 143.32	$ 3.81	$ 35.46	$ 41.33	$ 797.78
Both male and female
<18 years	$ 50.34	$ 8.00	$ 21.47	$ 0.97	$ 2.11	$ 1.69	$ 84.57
16–64 years	$ 470.77	$ 91.23	$ 146.07	$ 3.91	$ 42.27	$ 51.47	$ 805.73
>64 years	$ 369.42	$ 30.56	$ 56.85	$ 1.19	$ 9.01	$ 11.74	$ 478.76
All ages	$ 890.53	$ 129.79	$ 224.38	$ 6.07	$ 53.39	$ 64.90	$ 1,369.07

Note. Information on p-values for any comparisons between groups is available upon request.

In Table 5, we estimated the average costs of inpatient and outpatient services as well as of prescription drugs per patient among those who used these services (users). Of the total 268,672 patients being treated for CP by physicians in fiscal year 2021/22 (Table 1), 30,738 patients (11.4%) were hospitalized at least once in the same fiscal year. The most frequent diagnosis among these hospital admissions was of Mental and behavioural disorders (17.7%), followed by Injury, poisoning and certain other consequences of external causes (9.6%), Factors influencing health status and contact with health services (9.2%), Diseases of the digestive system (8.8%), and Diseases of the circulatory system (7.9%) (Supplementary Table S2). The average cost of inpatient services was CA$28,975.52 per user for all sex and age groups (Table 5). This cost among males was higher than in females (CA$35,116.80 vs CA$25,395.64) and highest in the oldest age group (CA$38,339.74 in males, CA$34,348.24 in females, and CA$36,027.13 in both), followed by the lowest age group (CA$3460.90 in males, CA$29,927.74 in females, and CA$31,721.58 in both).

Table 5.

Number (%) and average cost (CA$) of users of other health services among patients treated for chronic pain by physicians in Alberta fiscal year 2021/22.

Sex/age group	Inpatient services		Emergency visits		Outpatient clinic visits		Prescription drugs
	Number (%)	Cost/patient	Number (%)	Cost/patient	Number (%)	Cost/patient	Number (%)	Cost/patient
Male
<18 years	628 (6.6)	$ 34,460.90	3,290 (34.6)	$ 912.03	2,600 (27.3)	$ 3,398.61	7,133 (75.0)	$ 119.34
16–64 years	6377 (8.9)	$ 33,001.61	23,597 (33.1)	$ 1,408.81	19,673 (27.6)	$ 2,465.36	64,429 (90.3)	$ 285.30
>64 years	4313 (26.4)	$ 38,339.74	7,109 (43.5)	$ 1,794.92	8,273 (50.7)	$ 2,867.91	15,989 (97.9)	$ 271.34
All ages	11,318 (11.6)	$ 35,116.80	33,996 (35.0)	$ 1,441.47	30,546 (31.4)	$ 2,653.82	87,551 (90.1)	$ 269.23
Female
<18 years	959 (8.9)	$ 29,927.74	4,230 (39.4)	$ 1,182.35	3,184 (29.7)	$ 3,966.85	8,677 (80.8)	$ 96.11
16–64 years	12,516 (9.5)	$ 20,798.83	45,635 (34.5)	$ 1,270.66	42,842 (32.4)	$ 2,277.36	124,551 (94.1)	$ 265.69
>64 years	5941 (21.0)	$ 34,348.24	11,368 (40.1)	$ 1,565.42	13,292 (46.9)	$ 2,491.82	27,817 (98.1)	$ 266.21
All ages	19,416 (11.3)	$ 25,395.64	61,233 (35.7)	$ 1,319.28	59,318 (34.6)	$ 2,416.10	161,045 (93.9)	$ 256.65
Both male and female
<18 years	1587 (7.8)	$ 31,721.58	7,520 (37.1)	$ 1,064.08	5,784 (28.6)	$ 3,711.41	15,810 (78,1)	$ 106.59
16–64 years	18,893 (9.3)	$ 24,917.66	69,232 (34.0)	$ 1,317.74	52,515 (30.7)	$ 2,336.52	188,980 (92.7)	$ 272.38
>64 years	10,254 (23.0)	$ 36,027.13	18,477 (41.4)	$ 1,653.72	21,565 (48.3)	$ 2,636.10	43,806 (98.1)	$ 268.08
All ages	30,734 (11.4)	$ 28,975.52	95,229 (35.4)	$ 1,362.90	89,864 (33.4)	$ 2,496.90	248,596 (92.5)	$ 261.08

Note. Information on p-values for any comparisons between groups is available upon request.

Of the total 268,672 patients; 95,229 patients (35.4%) did visit ED, and 89,864 (33.4%) patients did visit outpatient clinics, at least once. The most frequent diagnosis among these ED and outpatient clinic visits was factors influencing health status and contact with health services (35.9%), followed by Mental and behavioural disorders (18.7%), Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (9.7%), Injury, poisoning and certain other consequences of external causes (6.0%), and Diseases of the digestive system (4.0%) (Supplementary Table S3). The average cost of ED visits per user was CA$1362.90 for all sex and age groups (Table 5). This cost among males was higher than in females (CA$1441.47 vs CA$1319.28) and highest in the oldest age group (CA$1794.92 in males, CA$1565.42 in females, and CA$1653.72 in both), followed by the age group of 18–64 years (CA$1408.81 in males, CA$1270.66 in females, and CA$1317.74 in both). The average cost of outpatient clinic visits per user was CA$2496.90 for all sex and age groups. This cost among males was higher than in females (CA$2653.82 vs CA$2416.10) and highest in the youngest age group (CA$3398.61 in males, CA$3966.85 in females, and CA$3711.41 in both), followed by the oldest age group (CA$2867.91 in males, CA$2491.82 in females, and CA$2636.10 in both).

Of the total 268,672 patients, 248,596 patients (92.5%) got at least one prescription (Table 5). On average, a user got 32.94 prescriptions of which opioid prescriptions accounted for 6.8% (Supplementary Table S4). The average cost of prescription drug per user was CA$261.08 for all sex and age groups (Table 5). This cost among males was higher than in females (CA$269.23 vs CA$256.65) and highest in the age group of 18–64 years for males (CA$285.30) and both sex groups (CA$272.38), followed by the age group of >64 years (CA$271.34 in males and CA$268.08 in both sex group). In females, the highest cost (CA$266.21) was found in the age group of >64 years, followed by the age group of 18–64 years (265.69) and the age group of <18 years (CA$96.11).

Discussion

Using the provincial Administrative Databases, we have estimated the treated prevalence of CP in Alberta, Canada, fiscal year 2021/22 at 6.0% accounting for 30% to 42% of the self-reported prevalence of CP previously estimated (Table 1). ⁵ This can be multifactorial, including lack of availability and accessibility of publicly funded services, people’s lack of awareness of the available services, lower utilization due to COVID-19 pandemic, and reliance on self-management, private services, and alternative treatments. Further studies to better understand these factors are warranted. Among others, further studies would also look at interventions improving self-management of CP, given the probability of self-management of CP being effective^21,22 and cost-effective, ²³ and the feasibility of digital self-management of CP interventions. ²⁴

In the current study, we have found a lower ratio between the treated and the self-reported prevalence in males, indicating that males with CP use physician services less frequently compared to their counterparts. This finding is consistent with previous studies. For example, Kazanjian et al. ²⁵ reported that females are twice as likely as males to report a regular family physician and Wong et al. ⁹ reported that the percentage of female patients with low back pain was higher among patients identified in administrative data compared to patients identified in self-reported population survey data.

There are two similar findings between the current study and our previous one. ⁵ One is that the prevalence of CP in females is higher than that in males, regardless of age groups. This may help inform target population and prioritization for future interventions against CP. The other is regarding costs. The current study has estimated total cost for the provincial health system at CA$1.37 billion per year, which is comparable to our previous estimate of CA$1.2 to CA$1.7 billion. With these results, the two studies support each other even though they used different methodologies. For better comparison, from the previous estimate, if we exclude components of cost that are not included in the current study, which is 7.4% of the cost for other services (such as nurse, physiotherapist, chiropractor, psychologist, social worker, and occupational therapist) and 5.8% for diagnostic imaging services, the previously estimated total cost will be CA$1.04 to CA$1.48 billion. Still, this is well comparable to the currently estimated total cost of CA$1.37 billion annually.

As an addition to the previously estimated average cost per person with CP (regardless being treated by health care providers or self-managed),⁵ in this study, we have estimated the average cost per patient with CP being treated by physicians at CA$5096 per year. This is more than 2 times of the HSU cost per average person per year in the general population (CA$2442), ²⁶ and similar to that of mental health disorder (CA$5323), ²⁷ in Alberta. Also, we have estimated the average costs per patient with CP being treated by physicians who also used inpatient, ED, outpatient clinic services, or prescription drugs (Table 5). This information would help future economic evaluations of interventions aiming to increase the proportion of self-managed people with CP locally, provincially, nationally, and internationally.

There are several limitations to be acknowledged. First, the treated prevalence of CP may be underestimated as the Alberta Health Care Insurance Plan does not cover services provided by nurses, physiotherapists, chiropractors, psychologists, social workers, or occupational therapists; therefore, the Practitioner Claims Database does not contain claims for these services used by patients with CP. On the other hand, the treated prevalence of CP may be overestimated as some billing codes for health service are not specific to CP. For example, the code of ‘08.19CW’, which accounted for 80% of all claims included in this study, is for telephone or secure videoconference with a patient for scheduled psychiatric treatment by a GP or pediatrician, or for a palliative care or a chronic pain visit. ¹⁰ However, this potential overestimate is likely small as the prevalence of CP is about 2 times higher than that of mental health diagnoses (20.1% vs 10.4%)^5,28 and many of people with mental health diagnoses have CP (up to 70% in some populations). ²⁹ Unfortunately, there were no uses of the ICD codes of CP to verify, so we suggest caution when interpreting the results. Second, as all diagnoses and prescription drugs linked to the unique lifetime identifier of the patients were included, this study is about costs of HSU of patients being treated for CP by physicians rather than simply the HSU costs of CP. Finally, this is a cross-sectional study that did not follow up with the patients to separate HSU between before and after the dates of visit to physicians. Also, that did not distinguish between new and existing patients with CP. A longitudinal study for these is warranted.

In conclusion, while the data using ICD codes of CP have not been available, physician claim billing codes can be used to identify patients who are likely to suffer from CP, enabling investigations of the epidemiological and economic burden of CP using healthcare administrative databases. Our findings suggest that the economic burden of CP is considerable. The comparison between treated and self-reported prevalence of CP shows many people with self-reported CP do not use the publicly funded health services. This can be multifactorial, including lack of availability and accessibility of publicly funded services, people’s unawareness about the available services, lower utilization due to COVID-19 pandemic, and reliance on self-management, private services, and alternative treatments. Further studies are warranted to inform future policies and health system initiatives aiming to reduce the burden of CP and improve lives of people living with it.

Ethical statement

Ethical approval

It was ethically approved by the Research Ethics Board (File # Pro00110848) on May 25, 2021.

Informed consent

As this study was a secondary analysis of previously collected data by Statistics Canada and Alberta Health, the Research Ethics Board at the University of Alberta indicated that obtaining additional informed consent was not required.

ORCID iD

Nguyen Xuan Thanh https://orcid.org/0000-0003-3984-7877