Evidence was synthesised using narrative review and meta-analysis. Monitoring of serum anti-TNF- (IFX or ADA) and/or of anti-drug antibody levels using test assays having a test-treatment algorithm. COMPARATOR Standard care. Results Any SLCO2A1 patient-related end Limaprost result, test agreement and cost-effectiveness estimations. The quality assessments used recognised checklists (Quality Assessment of Diagnostic Accuracy Studies-2, Cochrane, Philips and Consolidated Health Economic Evaluation Reporting Standards). Evidence was synthesised using narrative review and Limaprost meta-analysis. A Markov model was built in TreeAge Pro 2013 (TreeAge Software, Inc., Williamstown, MA, USA). The model experienced a 4-week cycle and a 10-yr time horizon, used a NHS and Personal Sociable Solutions perspective and used a linked evidence approach. Costs were modified to 2013/14 prices and discounted at 3.5%. RESULTS We included 68 out of 2434 and 4 out of 2466 studies for the medical performance and cost-effectiveness evaluations, respectively. Twenty-three studies comparing test methods were identified. Evidence on test concordance was sparse and contradictory, offering scant data for any linked evidence approach. Three studies [two randomised controlled tests (RCTs) and one retrospective observational study] investigated results following implementation of a test algorithm. None used the specified commercial ELISA immunoassay test packages. Neither of the two RCTs demonstrated medical good thing about a test-treatment routine. A meta-analysis of 31 studies to estimate test accuracy for predicting medical status indicated that 20-30% of test results are likely to be inaccurate. The four cost-effectiveness studies suggested that screening results in small cost reductions. In the economic analysis the base-case analysis showed that standard practice (no screening/restorative monitoring with the treatment checks) was more costly and more effective than screening for IFX. Level of sensitivity and scenario analyses offered related results. The probabilistic level of sensitivity analysis indicated a 92% likelihood the ‘no-testing’ strategy was cost-effective at a willingness to pay of 20,000 per quality-adjusted life-year. Advantages AND LIMITATIONS Demanding systematic reviews were undertaken; however, the underlying evidence foundation was poor or lacking. There was uncertainty about a linked evidence approach and a lack of gold standard for assay assessment. The only comparative evidence available for economic evaluation was for assays other than the treatment assays. CONCLUSIONS Our finding that testing is not cost-effective for IFX should be viewed cautiously in view of the limited evidence. Clinicians should be mindful of variance in overall performance of different assays and of the absence of standardised approaches to patient assessment and treatment algorithms. FUTURE WORK RECOMMENDATIONS There is substantial variance in the underlying treatment pathways and uncertainty in the relative performance of assay- and test-based treatment algorithms, which requires further investigation. There is very little research evidence on ADA or on drug monitoring in children with CD, and conclusions on cost-effectiveness could not become reached for these. STUDY Sign up This study is definitely authorized as PROSPERO CRD42014015278. FUNDING The National Institute for Health Research Health Technology Assessment programme. Full text of Limaprost this article can be found in Bookshelf..