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. Author manuscript; available in PMC: 2007 Aug 22.
Published in final edited form as: Bull World Health Organ. 2006 Apr 13;84(4):276–282. doi: 10.2471/blt.05.025379

Patterns of Hospital Transfer for Self-Poisoned Patients in Rural Sri Lanka – Implications for Estimating the Incidence of Self-Poisoning in the Developing World

Michael Eddleston 1,2, K Sudarshan 2, M Senthilkumaran 2, K Reginald 2, Lakshman Karalliedde 3, Lalith Senarathna 2, Dhammika de Silva 4, MH Rezvi Sheriff 2, Nick A Buckley 5, David Gunnell 6
PMCID: PMC1950595  EMSID: UKMS734  PMID: 16628300

Abstract

Objectives

Most data on self-poisoning in rural Asia have come from secondary hospitals. We aimed to examine how transfers from primary to secondary hospitals affected estimates of case fatality ratio (CFR), determine whether there was referral bias according to gender or poison, and estimate the annual incidence of all self-poisoning, and of fatal self-poisoning, in a rural developing world district.

Methods

Self-poisoning patients admitted to Anuradhapura General Hospital were reviewed on admission from July to December 2002. The medical notes of self-poisoning patients admitted to half of the surrounding peripheral hospitals were audited for the same period.

Findings

742 patients were admitted with self-poisoning to the secondary hospital; 81 died (CFR 10.9%). 483 patients were admitted to 17 surrounding peripheral hospitals. Six patients (1.2%) died in peripheral hospitals, 249 were discharged home, and 228 transferred. There was no effect of gender or age on likelihood of transfer; however, patients ingesting oleander or paraquat were more likely to be transferred. Estimated annual incidences of self-poisoning and fatal self-poisoning were 363 and 27 per 100,000 population, with an overall CFR of 7.4% (95% CI 6.0 to 9.0).

Conclusion

50% of patients admitted to peripheral hospitals were discharged home, showing that CFRs based on secondary hospital data are inflated. However, whilst the incidence of self-poisoning is similar to the UK, fatal self-poisoning is 3-fold more common in Sri Lanka than fatal self-harm by all methods in the UK. Population based data are essential for making international comparisons of case fatality and incidence, and for assessing public health interventions.

Introduction

Intentional self-poisoning is common in many parts of the world.1 However, its case fatality ratio (CFR) differs markedly between industrialised and developing worlds.2 For every 1000 self-poisoning patients admitted to European hospitals, fewer than five usually die.3 For every 1000 admitted to rural Asian hospitals, 100-200 usually die.4

Self-poisoning has been well researched in Sri Lankan secondary district hospitals over the last 25 years.5-15 Multiple studies have identified pesticides and yellow oleander seeds (containing cardiotoxic cardenolides 16,17) as being the most commonly ingested poisons and reported CFRs between 6.7 and 23.7%.7,10 The high CFR appears to be due to the ready availability of poisons that are more toxic and more difficult to treat than the poisons typically ingested in industrialised countries.14

The CFRs reported in the Sri Lankan studies5-15 above are higher than the national CFR reported by the Sri Lankan Ministry of Health - 3.9% in 2002.18 One reason is likely to be double counting of patients admitted to rural peripheral hospitals and then transferred to a secondary hospital.19 A second explanation might be that mildly poisoned patients are admitted to peripheral hospitals but not then transferred, raising the CFR in the secondary hospital due to the more severe case mix. Thus far, no studies have investigated the management and transfer of self-poisoned patients within a defined geographical area of an Asian country.

We aimed, in this study, to determine the pattern of patient transfer between hospitals of one Sri Lankan district to establish how these transfers influenced the CFR noted in the secondary hospital. We also aimed to determine whether there was bias according to gender or poison in the referral patterns, and to use the data to estimate the annual incidence of all self-poisoning, and of fatal self-poisoning, in this rural developing world setting.

Methods

The study was performed in Anuradhapura District, North Central Province (NCP), as part of a long term cohort study of patients over 11 years old with acute self-poisoning admitted to the medical wards of Anuradhapura General Hospital. Ethics approval was received from the Colombo Faculty of Medicine and Oxfordshire clinical research ethics committees. The cohort study was linked with an audit of patient admissions to peripheral hospitals that was carried out under the auspices of the Provincial Director of Health Services and included a continuing education component for health care workers in the peripheral hospitals.

At the 2001 census, the district had a population of 746,466, with 45.6% under the age of 25. The district has 34 peripheral health units with inpatient beds (figure 1) which all transfer poisoned patients to Anuradhapura General Hospital (a 1300 bedded secondary hospital with an intensive care unit) for further management, in particular mechanical ventilation for pesticide poisoning and cardiac pacing or anti-digoxin antitoxin for oleander poisoning.

Figure 1. Hospitals in Anuradhapura district.

Figure 1

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The hospitals chosen in this study have been ringed. The red cross marks Anuradhapura General Hospital to which all other hospitals transfer patients.

The official number of patients admitted for poisoning to hospitals in Anuradhapura District during July to December 2002 was obtained from the Medical Statistician at the Medical Statistics Unit, Colombo.

From 1st July to 31st December 2002, all patients admitted to the medical wards of Anuradhapura hospital with a history of self-poisoning were seen on admission by study doctors. The medical wards admit patients over eleven years. Personal data together with information on the poison ingested, treatment, and outcome was recorded prospectively. This study was stopped for three short periods during the six months; careful retrospective audit of multiple hospital records was performed to identify any patients admitted to the hospital during the six months who were not seen by the study doctors.

The retrospective audit of patients over eleven years old admitted to seventeen (half) of the district’s peripheral hospitals during July-December 2002 was collected by doctors during the first half of 2003. The 34 hospitals were ordered according to their bed number, paired off with the next centre in the list, and one randomly selected according to the toss of a coin. Seventeen hospitals were visited to review their medical records (table 1, figure 1). As part of the audit, cases were identified by manually searching all the medical records of each hospital for the six month study period. We have previously found the hospital ICD-10 based record system to contain inaccuracies19 and therefore chose to manually check every ticket rather than rely on official hospital records. Data on patient, poisoning, and outcome were extracted from each record.

Table 1.

Hospital characteristics and outcome for period Jul 1st to Dec 31st, 2002.

Unit Type No. of beds Size Time to AGH Poisoning Cases Died in PH Discharged alive from PH Transferred from PH % transferred (95% CI)
1 PU 21-40 S 45 41 0 20 21 51 (35 to 67)
2 PU 61-80 M 45 39 0 17 22 56 (40 to 72)
3 PU 41-60 M 60 36 1 22 13 34 (20 to 51)
4 DH 81-100 M 45 23 0 11 12 52 (31 to 73)
5 RH 21-40 S 120 6 0 2 4 57 (18 to 90)
6 RH 1-20 S 75 8 2 3 3 38 (9 to 76)
7 DH 101-150 L 45 67 1 50 16 24 (14 to 36)
8 RH 21-40 S 60 33 0 17 16 48 (31 to 66)
9 DH 151-200 L 120 57 0 32 25 44 (31 to 58)
10 RH 1-20 S 60 1 0 1 0 0 (0 to 98)
11 RH 41-60 M 45 44 0 30 14 32 (19 to 48)
12 RH 21-40 S 45 23 1 9 13 57 (34 to 77)
13 RH 1-20 S 20 14 0 9 5 36 (13 to 65)
14 RH 21-40 S 60 32 0 9 23 72 (53 to 86)
15 RH 41-60 M 120 6 1 5 0 0 (0 to 46)
16 PU 61-80 M 20 48 0 7 41 84 (70 to 93)
17 RH 21-40 S 30 5 0 5 0 0 (0 to 52)
All 483 6 249 228
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The hospitals were grouped according to size (based on bed number: small <40; medium 40-100, large >100).

Abbreviations: AGH, Anuradhapura General Hospital; DH, district hospital; L, large; M, medium; PH, peripheral hospital; PU, peripheral unit; RU, rural unit; S, small.

A list of patients admitted with self-poisoning to the 17 peripheral hospitals was generated, and patients marked as discharged alive, transferred, or died. This list was then compared to a list of patients admitted to Anuradhapura during the same period to find the ultimate outcome of transferred patients.

We used logistic regression models to investigate the effects of age, gender, poison type, and hospital characteristics on patient transfer using Stata.20 We took account of possible clustering effect of the seventeen hospitals by using the ‘cluster’ option of Stata. The hospitals were grouped according to size (based on bed number: small <40; medium 40-100, large >100) and case load (based on the number of patients admitted with self-poisoning: low <20; medium 20-40; high >40).

We used the data to estimate the annual incidence of self-poisoning. Since the data were collected over the last six months of 2002, we used prospectively collected data from Anuradhapura between March 2002 and April 2005 to study the effects of season on admissions rates.

Results

During the last six months of 2002, Ministry of Health records indicated that 1763 patients were admitted to hospitals in Anuradhapura District with a diagnosis of poisoning and that 39 died (CFR 2.2%, 95% CI 1.6 to 3.0).

Admissions and outcome in the secondary hospital

Between July and December 2002, 742 self-poisoned patients were admitted to Anuradhapura Hospital. Forty-one oleander-poisoned patients were transferred out of the district to tertiary hospitals for temporary cardiac pacing. Overall, 81 of 742 patients admitted to Anuradhapura hospital died (CFR 10.9%, 8.8 to 13.4). Ten of these patients were dead on admission; eleven died during or after transfer to a tertiary hospital.

Admissions and outcome in peripheral hospitals

Review of patient records in 17 peripheral hospitals (figure 1, table 1) revealed 485 patients admitted with self-poisoning during the six month study period. Two of these admissions were of patients who had been transferred back from Anuradhapura hospital after a period of ventilation in ICU. Both had initially been admitted to the primary hospital and then transferred to Anuradhapura; to avoid double counting, they were not further included in this analysis of primary admissions.

Of the 483 primary admissions, 280 (58.0%) were male and 203 female. 260 (53.8%) had taken pesticides, around half of which were organophosphorus (OP) pesticides. Oleander seeds and medicines had been ingested by 92 (19.0%) and 58 (12.0%) patients, respectively.

Only six patients (1.2%) died in the peripheral hospital. Five had ingested pesticides — three taking carbamates and two OPs, constituting 100% and 22% of the total number of identified deaths from these two pesticide classes, respectively. The sixth patient took an unknown poison.

249 patients (51.6%) were discharged home from the peripheral hospital while 228 (47.2%) were transferred for specialised care. 226 (99.1%) of the transferred patients could be traced after their arrival in Anuradhapura; 29/226 (12.8%) subsequently died.

Patterns of patient transfer

Similar proportions of males and females admitted to a peripheral hospital were transferred to a secondary hospital (men 135/280, 48.2%, women 93/203, 45.8%; odds ratio [OR] 0.91, 95% CI 0.61-1.34). There was no effect of age on the likelihood of transfer (OR for risk of transfer with each 10 year increase in age: 1.10, 95% CI 0.89-1.35).

Controlling for age and gender, we used logistic regression to assess whether poison ingested influenced the likelihood of transfer (table 2). Using OP poisoning as the reference category, patients ingesting hydrocarbons or medicines were significantly less likely to be transferred while patients with oleander or paraquat poisoning were more likely to be transferred.

Table 2.

Outcome of self-poisoned patients admitted to peripheral hospitals according to poison ingested.

Poison N Percent of all patients Discharged alive from PH Died in PH Transferred & survived Transferred & died Transferred. Outcome unknown Odds ratio for transfer using OP pesticides as the reference category OR (95% CI)
Hydrocarbon 25 5.2 20 0 5 0 0 0.30 (0.11 - 0.86)
Carbamate 27 5.6 15 3 9 0 0 0.58 (0.24 - 1.38)
Medicine 58 12.0 39 0 19 0 0 0.58 (0.36 - 0.94)
Unknown 48 9.9 27 1 19 1 0 0.81 (0.43 - 1.51)
Other pesticide 74 15.3 44 0 27 3 0 0.83 (0.60 - 1.14)
OP 135 28.0 70 2 54 7 2 1.00 (reference)
Unknown pesticide 6 1.2 2 0 3 1 0 2.11 (0.39 - 11.50)
Oleander 92 19.1 27 0 58 7 0 2.95 (1.71 - 5.12)
Paraquat 18 3.7 5 0 3 10 0 3.12 (0.88 - 11.03)
Overall 483 249 6 197 29 2
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Effect of hospital characteristics on patient transfer

We found marked variability in the proportion of poisoning patients transferred from different hospitals, varying from 0% in three small rural hospitals seeing 1, 5 and 6 poisoned patients to 90% in a peripheral unit seeing 49 patients. Using logistic regression and taking account of clustering, we found in simple models controlling for age and sex that the likelihood of transfer declined with distance (measured in time for transfer; OR 0.94 [0.81-1.08] for every 10 minute increase in time travelled).

Increased hospital size was associated with lower levels of transfer – the odds ratio for hospitals with more than 100 beds was 0.46 (0.22 to 0.95) compared to hospitals with less than 40 beds. However, admission of a large number of poisoning patients during the study period was associated with higher transfer rates – hospitals admitting 20-40 patients had OR of 2.66 (1.09 to 6.55) while those admitting more than 40 patients had 0R of 1.99 (0.63 to 6.23). The associations with hospital size and number of poisoning patients were strengthened in a model including all three hospital attributes; however, the association with transfer time was weakened.

Estimated annual incidence of all self-poisoning and of fatal self-poisoning

The 483 patients admitted to the 17 surveyed hospitals represent around half of the patients admitted to all 34 peripheral hospitals during six months, assuming that admission numbers in the non-sampled hospitals are the same as those in the randomly sampled hospitals (figure 2). We therefore estimate that around 966 patients with self-poisoning were admitted to peripheral hospitals across the district during the last six months of 2002.

Figure 2. Estimating number of hospital admissions.

Figure 2

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Data and calculations for estimating the number of primary self-poisoning admissions to all hospitals in Anuradhapura District between July and December 2002.

During the same six months, 742 patients were admitted to Anuradhapura hospital. 226 had been transferred from the 17 peripheral hospitals suggesting that around 452 (2 × 226) of the 742 patients had been transferred while 290 were admitted directly. The estimated number of patients admitted to all hospitals in the district during the six months was therefore 1256 (966 + 290, figure 2).

To estimate an annual incidence from this data, we first determined whether there were seasonal differences in patient admissions to Anuradhapura during the two halves of the year. From 31st March 2002 to 23rd April 2005, we had admission data for 424 days from the first half of the year (Jan to June) and 514 days from the second half (July to December). Admissions were 16% more common in the first half of the year: 4.79 vs. 4.12 patients per day. The proportion of patients admitted with oleander or OP poisoning in the first vs. second halves of the year were similar (25.9% vs, 27.9%, and 25.0 vs. 22.6%, respectively). Thus, taking into account the seasonal difference, the estimated total number of self-poisoning episodes within the district for the 12 month period was 2713 (figure 2).

Eighty-one patients died in Anuradhapura hospital during the second six months of 2002. Six additional deaths occurred in the 50% sample of peripheral hospitals studied, suggesting that a total of 93 (81 + [2 × 6]) patients died after first presentation to health care facilities in the whole district during these six months and 201 during the whole year (figure 2).

The population of Anuradhapura district in 2001 was 746,466, producing crude estimated annual incidences of 363 cases of self-poisoning and 27 fatal cases of self-poisoning per 100,000 population. The overall case fatality ratio for the district can thus be estimated as 7.4% (95% CI 6.0 to 9.0).

Discussion

This study shows that around 50% of self-poisoning patients admitted to small rural hospitals in Sri Lanka are managed in these hospitals and discharged home without being referred for secondary care. CFRs reported from secondary hospitals in Sri Lanka are artificially high.

By reviewing hospital records for a six month period in half of the hospitals referring to one district secondary hospital, we have been able to estimate the number of cases and deaths from self-poisoning in the district. From these data, we calculated a CFR of 7.4% for the district, compared to 10.9% found in the secondary hospital. Although lower than most estimates from hospital based studies, this CFR is still 10 to 20-fold higher than CFRs reported from industrialized countries.

Our estimates of cases, deaths, and CFR for the district from July to December 2002 were quite different to those reported in the government statistics. The official number of cases (1763) was 507 higher than our estimate of 1256. This is likely to be due in part to double counting of patients admitted to both primary and secondary hospitals (452 in our calculations). The official figure would also include non-intentionally poisoned patients. The proportion of patients admitted to Anuradhapura hospital for such poisoning is low (3% of poisoning cases21) but might account for some of the remaining difference.

The official number of deaths reported for the six months (39) was far lower than our estimate of 93 (which includes 81 prospectively recorded by us in Anuradhapura). This would be explained in part by patients dying after transfer out of the district to tertiary hospitals, and by the secondary hospitals not registering patients who died during transfer, but also suggests significant under-reporting by hospitals. As a result of te larger number of official cases, and fewer deaths, the official district CFR was only 30% of the CFR we calculated (2.2% vs. 7.4%).

These findings indicate that estimates of the number of fatal cases and the CFR for self-poisoning from either official accounts or secondary hospitals must be viewed with caution. It seems probable that such caution will apply to data from other Asian countries with a major self-poisoning problem. They also suggest that official suicide statistics may be substantial underestimates.

Our estimate is also likely to be an underestimate because we did not include patients who died before reaching hospital. However, an ongoing study in the province suggests that relatively few self-poisoned people currently die before first contact with health care providers (Eddleston, unpublished). This contrasts with data from Sri Lanka in the mid-1990s22 and China during 1998-200023 which showed that around 35% of pesticide deaths occurred before admission, markedly lowering the in-hospital CFR. The change in Sri Lanka is likely to be due to the banning of highly toxic pesticides, such as parathion, endosulfan and monocrotophos,19,24 that kill quickly and are responsible for many deaths in India and China.24,25

Relatively few deaths (an estimated 12 of 93; 12.9%) occurred in peripheral hospitals. Ten other patients died during transfer to Anuradhapura hospital, indicating that the majority of self-poisoning deaths (71/93, 76%) occurred after patient admission to the medical wards of the district hospital. This suggests that the transfer triage system is largely successful at identifying patients with life-threatening poisoning (irrespective of whether they can currently be saved or not).

Three of the six deaths occurring in the peripheral hospitals were due to carbamate poisoning, representing all deaths from carbamates in this study. By contrast, only two of the deaths were due to OP pesticides and none were due to paraquat. This may be because of a slower onset of action of OP pesticides and paraquat, the former due to the relatively slow activation of the OPs now available in Sri Lanka, compared to the carbamates which do not need activation and may be rapidly lethal.26 Alternatively, carbamate poisoning may be perceived as less dangerous than other forms so that carbamate poisoned patients may not transferred until too late.

We did not find any effect of either age or gender on rates of transfer by peripheral hospitals. However, referral was more likely for patients with oleander or paraquat poisoning compared to those with other forms of pesticide poisoning. This is likely to be due to the need of oleander patients for cardiac pacing and the very poor prognosis for paraquat poisoning.

Patients admitted to larger hospitals with more facilities and doctors were less likely to be transferred. However, hospitals seeing larger numbers of patients transferred more patients, possibly because they used up resources. A qualitative study of patient management in different hospitals may shed more light on this issue.

This study has allowed us to estimate an incidence of around 363/100,000 for intentional self-poisoning in a rural Sri Lankan district. The figure is likely to be an under-estimate since some patients will have died before reaching medical care and some may have taken a small overdose but not presented to hospital. However, we think it likely to be reasonably accurate since community studies show that practically all poisoned patients are brought to hospital by relatives and all patients presenting to hospital in Sri Lanka are admitted (ref 27 and Maracek, unpublished observations).

Our estimate is similar to that reported from a division of Anuradhapura district in 1991-4 (260-290/100,000)28 but double the 163/100,000 estimated from a study of patients admitted to two government hospitals in Embilipitiya district during 1998-1999.27 It is unclear whether the difference with Embilipitiya is due to patients admitted to peripheral hospitals being missed or a reduced incidence of self-harm in this southern district. There have been no campaigns in Embilipitiya district to lower self-harm rates during this period.

The incidence of admission for self-poisoning in the UK is around 140/100,000.29 Since only around half of patients presenting to hospital in the UK are admitted,30 this suggests that the incidence of hospital presentations for self-poisoning is near 300/100,000. The proportion of all acts of self-poisoning that present to hospital in the UK is not known; however, a study by Hawton and colleagues suggests that as many as 75% of overdoses in adolescents might not present to hospital, raising the estimated incidence of self-poisoning in the UK even further.31

The incidence of fatal self-poisoning in this rural district (27/100,000) was around three times the fatal self-harm incidence for all methods in the UK (8.6/100,00032). However, it is around half of that recently reported from southern India33 where highly toxic pesticides are still widely available.24

In conclusion, this study suggests that the incidence of self-poisoning in this rural developing world district is similar to or lower that of the UK, but that the CFR for self-poisoning is at least 10-fold higher and the incidence of fatal self-poisoning 3-fold higher than that of all fatal self-harm in the UK. Knowledge about patterns of patient management and transfer within districts are important for international comparisons of case fatality and incidence, for interpreting time trends, and for assessing the impact of public health interventions.

Acknowledgements

We thank the Provincial Director of Health Services, NCP, for his encouragement and help with this study and audit, Samitha Egodage for his work, and Mr Saddhananda, Senior Statistician, Medical Statistics Unit, for the official hospital admission statistics. ME is a Wellcome Trust Career Development Fellow, funded by grant GR063560. The South Asian Clinical Toxicology Research Collaboration is funded by a Wellcome Trust/National Health and Medical Research Council International Collaborative Research Grant GR071669.

Footnotes

Contributions

ME set up the cohort study in Sri Lanka, initiated this study, did the analysis and wrote the first draft. KS, MS, and KR saw patients in the secondary hospital, visited the peripheral hospitals, and set up the databases. LK visited all peripheral hospitals to provide continuing education and assess hospital management of poisoned patients. LS organised the secondary hospital and peripheral hospital studies. DdS provided input from the Provincial Director’s office for the audit. MSRH is the senior Sri Lankan coordinator of the Ox-Col studies. NAB designed the original cohort study. DG did the analysis. All authors saw and commented on earlier drafts of the paper and approved the final submitted paper.

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