Novel predictors of neurosyphilis among HIV-negative syphilis patients with neurological symptoms: an observational study

Table 3 Screening performance of parallel testing of serum RPR and serum TPPA for S-NS

Parallel testing format	Identification of S-NS			Identification of confirmed neurosyphilis			Identification of probable neurosyphilis
Parallel testing format	Sensitivity (%)	Specificity (%)	NPV (%)	Sensitivity (%)	Specificity (%)	NPV (%)	Sensitivity (%)	Specificity (%)	NPV (%)
RPR≥1:4, TPPA≥1:2560^a	87.8	72.5	84.9	97.5	60.8	98.0	70.1	72.5	86.6
RPR≥1:2, TPPA≥1:2560	92.6	55.6	87.6	99.2	45.7	99.1	80.6	55.6	88.4
RPR≥1:4, TPPA≥1:1280	93.1	58.7	89.0	99.2	47.6	99.2	82.1	58.7	89.7
RPR≥1:2, TPPA≥1:1280	95.8	46.4	91.2	100.0	37.0	100.0	88.1	46.4	91.2

S-NS symptomatic neurosyphilis, N-NS syphilis/non-neurosyphilis, RPR rapid plasma reagin, TPPA T. pallidum particle agglutination, PPV positive predictive value, NPV negative predictive value
^aA positive screening result was defined as either serum RPR titer ≥1:4 or serum TPPA titer ≥1:2560, or both. And by this analogy

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