Wallach’s Interpretation of Diagnostic Tests, now in its Ninth Edition, has been completely revised and updated by a new author team from the Department of Hospital Laboratories, UMass Memorial Medical Center faculty, who are carrying on the tradition of Jacques Wallach’s teachings. This text serves as a practical guide to the use of laboratory tests which aids physicians in using tests more effectively and efficiently by offering test outcomes, possible meanings, differential diagnosis, and summaries of tests available. The book has been reorganized into 2 sections. The first section is devoted to an alphabetical listing of laboratory tests while stressing the integration of the clinical laboratory in the clinical decision making process. Test sensitivity, specificity, and positive and negative infectious disease probabilities are included whenever appropriate. Microbiology tests are listed in a separate chapter. The second section is devoted to disease states. Where appropriate, a patient’s chief complaint and/or physical findings are initially presented with subsequent discussions focused on discrete disease states as they relate to a patient’s chief complaint. Current molecular diagnostic testing, cytogenetics, common pitfalls, test limitations, and identification of appropriate tests for specific clinical presentations are also addressed.