A Lab Test and Algorithms for Identifying Clients at Risk for Treatment Failure  Corinne Hannan, Michael J. Lambert, Cory Harmon, Stevan Lars Nielsen, David W. Smart, and Kenichi Shimokawa Brigham Young University  Scott W. Sutton Emory and Henry College Many branches of medicine rely heavily on lab tests to monitor client treatment response and use this information to modify their treatment. By contrast, those who offer psychological interventions seldom rely on for- mal assessments (lab tests) to monitor their clients’ response to treatment. Data are presented that demonstrate that clinicians rarely accurately pre- dict who will not benefit from psychotherapy. This finding is contrasted with the use of a questionnaire (lab test data) and decision rules on the basis of a client’s expected progress. Results have indicated that formal methods of monitoring were able to identify 100% of the patients whose condition had deteriorated at termination, and 85% by the time they had attended three treatment sessions. Practitioners are encouraged to con- sider formal methods of identifying the deteriorating client. © 2004 Wiley Periodicals, Inc. J Clin Psychol/In Session 61: 155–163, 2005. Keywords: deterioration; negative outcomes; Outcome Questionnaire-45; identification of treatment failure; outcomes management; psychotherapy outcome Lab tests used in conjunction with empirically based cut scores and decision trees are regularly employed in various branches of medicine. These tests are used particularly when clinical judgment is involved in the interpretation of diverse information because lab test results are generally more accurate than more subjective methods. In the diagno- sis and treatment of prostate cancer, for example, a physician commonly begins by taking Correspondence concerning this article should be addressed to: Michael J. Lambert, Department of Psychology, 272 TLRB, Brigham Young University, Provo, UT 84602; e-mail: michael_lambert@byu.edu. JCLP/In Session, Vol. 61(2), 155–163 (2005) © 2005 Wiley Periodicals, Inc. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jclp.20108