Influencing factors of false-positive serological reaction of syphilis / 中华传染病杂志

ABSTRACT

Objective:To explore the influencing factors of false-positive serological reaction of syphilis.Methods:A total of 166 patients with false-positive serological reaction of syphilis (false-positive group), 145 patients diagnosed with early syphilis without treatment (positive control group) and 124 persons undergoing entry physical examination (negative control group) were included from January 2017 to February 2020 in Beijing Tongren Hospital, Capital Medical University. The gender, age and underlying diseases of the three groups were compared. Logistic regression was used to analyze the influencing factors of false-positive serological reaction of syphilis. The efficacies of chemiluminescence immunoassay (CLIA) and toluidine red unheated serum test (TRUST) were compared. Paired t test or chi-square test was used for statistical analysis. Results:In the false-positive group (166 cases), the age of 117 cases were more than 50 years old and 49 cases <50 years old. There were significant differences in age ((53.1±13.8) vs (24.7±2.8), t=22.56, P<0.01), autoimmune disease (36.7%(61/166) vs 6.5%(8/124), χ2=35.93, P<0.01), hepatitis (9.6%(16/166) vs 3.2%(4/124), χ2=4.92, P=0.026) and tumor (6.6%(11/166) vs 0.8%(1/124), χ2=4.68, P=0.030) between the false-positive group and the negative control group. There were significant differences in gender (there were 91(54.8%) males and 75(45.2%) females in the false-positive group, and 103(71.0%) males and 42(29.0%) females in the positive control group, χ2=8.67, P=0.003), age ((53.1±13.8) vs (34.4±12.9), t=20.13, P<0.01) and autoimmune disease (36.7%(61/166) vs 6.9%(10/145), χ2=39.14, P<0.01) between the false-positive group and the positive control group. Multivariate logistic regression analysis showed that gender (odds ratio ( OR)=2.692, 95% confidence interval ( CI) 1.504-4.816, P=0.001), age ≥50 years old ( OR=30.512, 95% CI 15.959-58.335, P<0.01), autoimmune disease ( OR=2.677, 95% CI 1.258-5.695, P=0.011) and hepatitis ( OR=4.408, 95% CI 1.799-10.799, P=0.001) were the influencing factors of false-positive serological reaction of syphilis. In the false-positive group, the positive rate of TRUST was 84.9% (141/166), which was higher than that of CLIA (23.5%(39/166)). The difference was statistically significant ( χ2=126.25, P<0.01). CLIA was 1.0-10.0 cut off index (COI) in 36 patients, and >10.0 COI in three patients.The difference was statistically significant ( χ2=52.51, P<0.01). The titers were ≤1∶4 in 139 patients and≥1∶8 in two patients with TRUST positive.The difference was statistically significant ( χ2=262.35, P<0.01). The sensitivity and specificity of CLIA were 95.2% and 96.0%, respectively, and those of TRUST were 77.2% and 91.1%, respectively. Conclusions:The influencing factors of false-positive serological reaction of syphilis include patients age ≥50 years and with autoimmune disease or hepatitis. The false-positive rate of TRUST is significantly higher than CLIA.