Table 1.

Description of study design characteristics.

AUTHOR LAST NAME	YEAR OF PUBLICATION	NUMBER OF PARTICIPANTS	STUDY DESIGN	INTERVENTION(S) EVALUATED	HOW WAS CHRONIC PAIN MEASURED?	HOW WAS CHRONIC PAIN DEFINED	PATIENTS ON PRESCRIBED OPIOIDS OR ADJUNCT PAIN TREATMENTS
Peles	2005	170	Cross-sectional	High-dose methadone (≥60 mg/day)	BPI	Current pain that lasted for at least 6 months	Not reported
Dhingra	2012	489	Cross-sectional	High-dose methadone (≥60 mg/day)	BPI	“Clinically significant pain” was defined by an average pain intensity during the past week of >5 or an average pain interference score during the past week of >5.	82% of the sample is receiving an adjunct pain therapy (not reported by pain status)
Barry	2009	150	Cross-sectional	High-dose methadone (≥60 mg/day)	BPI	Respondents’ answers to BPI items were used to classify them into one of three pain groups: a) “chronic severe pain” (ie, pain lasting at least 6 months with moderate to severe pain intensity or significant pain interference, respondents who had pain lasting at least 6 months and who scored 5 or higher on the item pertaining to the worst pain intensity in the last 7 days or on any of the items relating to pain interference in the last 7 days were considered to exhibit chronic severe pain; b) “some pain” (ie, pain reported in past week but not CSP); and c) “no pain” (ie, no pain reported in the past week and no CSP).	Not reported
Bounes	2013	151	Cohort study (prospective or retrospective)	Low-dose methadone (<60 mg/day), Low-dose buprenorphine (<16 mg/day)	A Visual Analog Scale (VAS) or Numerical Rating Scale (NRS) was used to assess and quantify the intensity of acute pain at the time of admission, after pain management, and just before hospital discharge.	Acute pain scores rated from 0 to 10 were obtained indiscriminately from one or the other measurement tool. Acute pain exposure was defined as a pain score greater than 0 at the time of admission on any of the rating scales.	Patients without pain: 0% Patients with pain: 5% Total sample: 3%
Chakrabarti	2010	69	Cross-sectional	High-dose Suboxone® (buprenorphine ≥16 mg/day + naloxone)	EQ-5D: a measure of health status from the EuroQol	Degree of pain 1 week before induction, measured as pain or discomfort experienced “today” and coded as 0 = no pain, 1 = some pain, or 2 = extreme pain	Not explicitly reported (although they removed any patients with prescription medications which may interfere with dosing)
Dennis	2014	235	Cross-sectional	High-dose methadone (≥60 mg/day)	Self-report	Participants were categorized as having chronic and/or comorbid pain if they indicated they were currently experiencing or have been diagnosed with chronic pain	Participants on prescribed opioids were removed from analyses
Dreifuss	2013	360	Cross-sectional	High-dose Suboxone® (buprenorphine ≥16 mg/day + naloxone)	The pain and analgesic use history opiate	Not described	Not reported (only brief discussion in study selection criteria that they included patients currently prescribed opioids with approval of attending physician)
Dunn	2014	227	Cross-sectional	High-dose methadone (≥60 mg/day)	BPI	Chronic pain was defined as endorsing question 1 of the BPI, which asked, “Have you had pain other than everyday kinds of pain today?”	Not reported
Fox	2012	82	Cohort study (prospective or retrospective)	High-dose buprenorphine (≥16 mg/day), low-dose buprenorphine (<16 mg/day)	BPI	The Brief Pain Inventory (BPI) asked: “Please rate your pain during the last week by selecting the one number that best describes your pain on the average.” Participants were given a visual analog scale from 0 to 10, with 0 labeled as “no pain” and 10 as “pain as bad as you can imagine.” Similar to prior studies, participants reporting pain scores of ≥5 at the initial interview were considered to have “baseline pain”; those reporting pain scores of ≥5 at all follow-up visits were considered to have “persistent pain”	No participants were on prescribed opioids for pain
Jaimison	2000	248	Cross-sectional	High-dose methadone (≥60 mg/day), low-dose methadone (<60 mg/day)	Self-reported measure (Survey created for study)	Not described	77% of sample report being prescribed medications for pain, itemized list of different adjunct therapies is provided (summarized for patients with and without pain). Although no adjusted analyses are performed to evaluate the mediating effects of these on study outcomes
Neumann	2013	54	Randomized controlled trial	Low-dose methadone (<60 mg/day), low-dose Suboxone® (buprenorphine <16 mg/day + naloxone)	Confirmed by clinical examination and diagnostic imaging	The diagnosis of a chronic pain condition originating from the spine or large joints was confirmed by clinical examination and the use of diagnostic imaging (eg, radiographs, computed tomography scan, magnetic resonance imaging)	Not reported (patients advised not to continue taking prescribed opioids during course of study)
Potter	2015	252	Cohort study (prospective or retrospective)	Low-dose Suboxone® (buprenorphine <16 mg/day + naloxone)	BPI	Not described	Not reported (only brief discussion in study selection criteria that they included patients currently prescribed opioids with approval of attending physician)
Rosenblum	2003	390	Cross-sectional	High-dose methadone (≥60 mg/day)	BPI	To operationally define a subpopulation of patients with chronic pain that was relatively likely to be clinically significant, an index of “chronic severe pain” was defined as a score of 5 or higher on the BPI item “worst pain in the past week” or of 5 or higher on the BPI pain interference scale, and pain duration for at least 6 months.	Not reported by pain status
Trafton	2004	251	Cross-sectional	High-dose methadone (≥60 mg/day), low-dose methadone (<60 mg/day), high-dose levoacetylmethadol (LAAM) (≥85 mg/day), low-dose levomethadyl acetate hydrochloride (LAAM) (<85 mg/day)	SF-36V Quality-of-Life Index	Reported pain levels were taken from answers to the SF-36V question “How much body pain have you experienced in the last 4 weeks?” Patients answered either “none” (n = 45), “very mild” (n = 28), “mild” (n = 48), “moderate” (n = 60), “severe” (n = 56) or “very severe” (n = 13). For analyses patients were split into those reporting none to mild pain (no-pain group, n = 121) and those reporting moderate to very severe pain (pain group, n = 129).	Not reported