Evidence-based laboratory medicine - a guide for critical evaluation of in vitro laboratory testing.

Evidence-based laboratory medicine (EBLM) is an essential part of modern laboratory medicine practice. This review presents a guide for better understanding and implementing the EBLM process. The process of EBLM begins with development of a clinically relevant question. Tools for assisting in question formulation include the Patient Intervention Comparator and Outcome (PICO) or Case Assay Predicate and Outcome (CAPO) strategies. Locating evidence that addresses the question is performed using resources available on the internet. Systematic reviews that have objectively collated evidence addressing the question can be particularly useful. The evidence collected must be critically appraised using checklists developed for this purpose. Diagnostic performance of tests is frequently stated in terms of sensitivity, specificity, negative and positive predictive values, and the diagnostic odds ratio. Evaluating 95% confidence limits is important for interpretation. Likelihood ratios for tests in disease states are also important for converting pre-test probabilities to post-test probabilities using Bayes Theorem. Tools such as Receiver Operator Characteristic curves and Fagan's diagram are important analytical and visual aids. Laboratorians must give thoughtful consideration into conveying information to clinicians in a useful format. Evidence-based guidelines and collaboration with clinicians are important for development of local care paths. Auditing the effectiveness of implemented care paths is an important part of quality management. In conclusion, effective use of EBLM can benefit patients by helping laboratorians provide the best-available information in the clinically relevant time frame. Presenting the information appropriately maximizes clinical application of the best evidence.