- Last Update On : 2013-01-31
Routine laboratory tests are often ordered regardless of findings elicited from the medical history or physical examination. Ordering tests indiscriminately is costly, counterproductive and may increase patient risk. Reference ranges for laboratory tests are usually chosen to include 95% of healthy individuals. Therefore, 5% of test results from patients without disease will fall outside the reference range. For example, if hemoglobin levels were measured on100 healthy individuals, 5 would be expected to have abnormal results. Ordering several tests further increases the chances of a healthy person having at least one abnormal result. If two tests are ordered on a healthy individual, the chances of both being normal are 0.95 X 0.95 = 0.90. That means there is a 10% probability that at least one of the results will be abnormal. The chance of at least one test being abnormal increases with the number of tests ordered. When ten tests are ordered, there is a 40% probability of at least one result being abnormal.
Patients can be harmed directly from follow-up of false positive or borderline positive results. Often times, additional confirmatory tests are ordered and patients may be referred to a specialist, who may perform an invasive procedure. Patients can be harmed indirectly when false positive tests divert a physician’s attention from more important patient care issues or unnecessarily result in postponement of a therapeutic procedure. Clearly, it is better medical practice to perform only those tests that provide more benefit for the patient than risk. Today’s health care environment mandates that pathologists and laboratory managers play an active role in promoting cost-effective utilization of laboratory services.