False-Negative Syphilis Screening Due to Change in Temperature

Inaccurate test results for syphilis may cause an individual to experience serious effects.Investigate potential sources of error and test limitations causing false-negative reactions.In 5 months, two laboratories screened 2,232 patients for syphilis by the Rapid Plasma Reagin (RPR) test.The hospital laboratory reported 5.3% (64/1,210) of patients' test as reactive on initial screening, and the research laboratory found 6.4% (78/1,210) reactive. Fourteen reactive patients were incorrectly reported negative by the hospital laboratory, as confirmed by both laboratories. A refrigerated centrifuge in the hospital laboratory possibly caused sera to be cooled before testing, producing false-negative results. When its temperature was adjusted from 4 degrees C to 27 degrees C, an additional 1,022 samples tested were consistent between the two laboratories.Cold temperature produces false-negative reactions for syphilis screenings in patients' samples with titers < 1:4 dilution. Patients' samples with titers > or = 1:16 dilution were not affected. According to this study, incorrect temperatures for test sera can alter testing outcomes. Therefore, test manufacturer's directions must be strictly followed.