False-negative syphilis screening due to change in temperature.
OBJECTIVE
Inaccurate test results for syphilis may cause an individual to experience serious effects.


OBJECTIVE
Investigate potential sources of error and test limitations causing false-negative reactions.


METHODS
In 5 months, two laboratories screened 2,232 patients for syphilis by the Rapid Plasma Reagin (RPR) test.


RESULTS
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.


CONCLUSIONS
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.
el-Zaatari
M M
MM
Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston.
Martens
M G
MG
D015982:Bias; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000097:blood* / Q000453:epidemiology / Q000517:prevention & control; D012034:Refrigeration; D013048:Specimen Handling / Q000379:methods*; D013587:Syphilis / Q000097:blood* / Q000453:epidemiology / Q000517:prevention & control; D013588:Syphilis Serodiagnosis / Q000379:methods*; D013696:Temperature