Spotlight on Test Utilization: Should the Qualitative Serum Pregnancy Test Be Considered Obsolete?
Rapid testing for the qualitative detection of human chorionic gonadotropin (hCG) in urine or serum using point-of care (POC) test devices is frequently performed in health care settings to identify a possible pregnancy. Qualitative urine hCG tests are attractive because the urine sample requires no special processing and the tests are granted waived status by the Clinical Laboratory Improvement Amendments (CLIA). As such, testing can truly be performed at the POC by any health care provider. In contrast, qualitative serum hCG tests are categorized by CLIA as moderately complex because they require the collection of a whole blood specimen that must be centrifuged before testing to obtain the serum sample. The need to perform qualitative hCG testing in serum has been questioned for several reasons. First, owing to the sample type, testing cannot be performed at the POC. Second, clinical laboratories are often able to perform quantitative serum hCG tests that have relatively short analytic times (10-20 minutes). Third, quantitative hCG tests can measure hCG at a concentration lower than the detection thresholds claimed by qualitative tests (~1 vs 10-25 IU/L, respectively). Fourth, because the only clinical use of a qualitative serum hCG test is to detect (or rule out) a possible pregnancy, it can be argued that the most analytically sensitive test available (ie, quantitative) should be used.
David G. Grenache, PhD
Medical Director, Special Chemistry Laboratory, ARUP Laboratories
Associate Professor of Pathology, University of Utah School of Medicine
Dr. Grenache is the director of the Special Chemistry Laboratory at ARUP and is a certified diplomate by the American Board of Clinical Chemistry. Dr. Grenache earned his PhD from Worcester Polytechnic Institute in Worcester, Massachusetts and completed a clinical chemistry fellowship at Washington University, St. Louis.
Larissa V. Furtado, MD
Co-Chief Resident of Pathology, University of Utah School of Medicine
Dr. Furtado is currently the Co-Chief Resident of Pathology and Cell Biology at the University of Utah School of Medicine. Dr. Furtado will begin a Molecular Genetic Pathology fellowship at the University of Michigan in Ann Arbor, Michigan in July of 2012.
- Describe why the need for qualitative serum human chorionic gonadotropin (hCG) testing has been questioned.
- Describe the diagnostic performance of qualitative and quantitative hCG tests.
- Discuss reasons for and against discontinuing the use of qualitative serum hCG tests.