Table C-19KQ 3c: Association between TPMT enzymatic activity and thiopurine toxicity – risk of bias assessment, part 2

StudyAvoidance of selection biasMethods to control confoundingAppropriateness of TPMT activity testApplicabilitySummary risk of bias assessment
Ansari, 200229UnclearNoYesUnclear - Uncertain representativeness of patients with IBD.Fair – Unclear if outcome assessment is biased. Methods to control confounding not described. Avoidance of selection bias is unclear.
Czaja, 200648UnclearNoYesUnclear - Uncertain representativeness of patients with autoimmune hepatitisFair - Unclear if outcome assessment is biased. Avoidance of selection bias is unclear. Unclear reliability and suitability of TPMT activity assay.
Firooz, 200849UnclearNoYesUnclear - Uncertain representativeness of pemphigus vulgaris patients. Excluded patients for whom adverse event of clinical data were not available.Fair - Unclear if outcome assessment is biased. No methods to control confounding. Unclear similarity of groups. Adequacy of sample size is unclear.
Gisbert, 200650UnclearUnclearYesUnclear - Uncertain representativeness of patients with IBD.Fair - Unclear if outcome assessment is biased. Methods to control confounding not described. Unclear similarity of groups.
Hindorf, 200632YesNoYesUnclear – Uncertain representativeness of patients with IBD. Excluded patients for whom TPMT metabolite or enzymatic assessment had not been previously performed.Fair - Unclear if outcome assessment is biased. Potential confounding by age, use of corticosteroids and 5-ASAs.
Kader, 200051NoNoUnclearUnclear - Uncertain representativeness of patients with IBD.Poor - Unclear reliability and suitability of TPMT activity assay. Uncertain representativeness of pediatric patients. Unclear similarity of groups.
Lennard, 198952NoNoYesUnclear - Uncertain representativeness of patients with chronic autoimmune disease.Poor - Unclear if outcome assessment is biased. Methods to control confounding not described. Avoidance of selection bias is unclear. Unclear similarity of groups. Uncertain representativeness of autoimmune disorder patients.
Okada, 200537UnclearNoYesUnclear - Uncertain representativeness of Japanese patients with SLE.Fair - . Avoidance of selection bias is unclear. Small sample size. Unclear if blinded outcome assessment and TPMT activity testing.
Schedel, 200653UnclearNoUnclearUnclear - Uncertain representativeness of patients with chronic autoimmune disease.Fair - Unclear if outcome assessment is biased. Avoidance of selection bias is unclear. Uncertain representativeness of patients with autoimmune disease. Unclear reliability and suitability of TPMT activity assay.
Shah, 200854UnclearNoUnclearUnclear - Uncertain representativeness of patients with IBD.Poor - No methods to control confounding. Unclear similarity of groups. Unclear reliability and suitability of TPMT activity assay. Adequacy of sample size is unclear. Unclear if blinded outcome assessment and TPMT activity testing.
Snow, 199539NoNoYesUnclear – Uncertain representativeness of patients with autoimmune dermatologic conditionsPoor – Unclear similarity of groups. Small sample size. Unclear if blinded outcome assessment and TPMT activity testing. Methods to control confounding not described. Avoidance of selection bias is unclear.
Stassen, 200940UnclearNoYesUnclear – Uncertain representativeness of patients with anti-neutrophil cytoplasmic antibody associated vasculitisFair - Unclear if outcome assessment is biased. Unclear similarity of groups. Methods to control confounding not described.
Stocco, 200541UnclearNoYesUnclear - Uncertain representativeness of patients with IBD.Fair - Unclear if outcome assessment is biased. Potential for selection bias.
Stolk, 199855NoYesYesUnclear - Uncertain representativeness of patients with rheumatoid arthritis. Strict inclusion criteria.Fair - Unclear if outcome assessment is biased. Avoidance of selection bias is unclear. Small sample size.
von Ahsen, 200543UnclearNoYesUnclear - Uncertain representativeness of patients with IBD. Excluded those likely to experience adverse events.Fair – Avoidance of selection bias is unclear. Uncertain representativeness of adult IBD patients. Unclear if blinded outcome assessment and TPMT activity testing. Potential for selective outcome reporting bias.
Winter, 200744UnclearNoYesUnclear - Uncertain representativeness of patients with IBD. Included only those patients with a history of thiopurine use.Fair - Unclear if outcome assessment is biased. Unclear similarity of groups.

Abbreviations: 5-ASA = 5-aminosalicylates; IBD = inflammatory bowel disease; SLE = systemic lupus erythematosus; TPMT = thiopurine methyltransferase.

From: Appendix C, Evidence Tables

Cover of Assessment of Thiopurine Methyltransferase Activity in Patients Prescribed Azathioprine or Other Thiopurine-Based Drugs
Assessment of Thiopurine Methyltransferase Activity in Patients Prescribed Azathioprine or Other Thiopurine-Based Drugs.
Evidence Reports/Technology Assessments, No. 196.
Booth RA, Ansari MT, Tricco AC, et al.

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