A Clinical Comparison Between the Friedman Test and an in Vitro Test for Pregnancy.

Latex pregnancy tests were performed on 737 urine samples submitted to a hospital laboratory for Friedman tests. Clinical confirmation of the diagnoses was obtained in 666. Nine Friedman and 31 latex tests were falsely positive in 199 samples having specific gravities over 1.015. Each test gave four false-positive results in 65 samples with specific gravities under 1.015. Between six and 13 weeks of gestation, nine Friedman and 45 latex tests were negative in 176 samples with specific gravities above 1.015; below 1.015, five Friedman and 15 latex tests were false in 42 samples. At other stages of pregnancy, seven Friedman and 18 latex tests were negative in 56 samples with specific gravities over 1.015 and, under 1.015, nine samples had four negative latex tests.The latex test requires careful control and is less reliable than the Friedman test.