Update on pregnancy testing.

Laboratory testing is an extension of the physical examination, reaching sites that are otherwise inaccessible to the examiner. Pregnancy testing is one such diagnostic extension. Like physical examination, it must be used carefully. In choosing a pregnancy test for office use, many factors must be considered, so that accurate information will be available for patient management. Such factors as the technical skills and training of the office staff performing the test, shelf life of the test, need to refrigerate reagents, and frequency of usage are all important considerations. Test results must always be correlated with specific patients and clinical findings, and at times, doubts may be allayed by simply retesting patients with negative or equivocal results at a later time (currently a matter of days instead of weeks). Recent developments in pregnancy testing have been directed toward improved sensitivity and specificity, as well as speed, simplicity, and reduced cost. The clinical issue of greatest interest to most primary care physicians is the early diagnosis of normal pregnancy, where "early" may be defined as prior to the first missed menses. Diagnosis in the first 21 days of gestation is currently possible with more sensitive methods, and especially with enzyme-linked immunoassay. In this regard, because of its easy methodology and basic reliability, the enzyme-linked immunoassay may well become the new standard for office pregnancy testing.