Background: The diagnosis of neurosyphilis (NS) is challenging due to the requirement of lumbar puncture and time-consuming cerebrospinal fluid tests. Therefore, a convenient high-accuracy diagnostic nomogram for NS is warranted.
Methods: This cross-sectional study (108 patients) aimed to construct diagnostic models for diagnosing NS with data gathered between September 2015 and January 2020 at Western China Hospital of Sichuan University. We constructed two types of diagnostic models using 108 training samples: 1) symptoms and toluidine red unheated serum test (TRUST) (basic model) and 2) the combined model of symptoms, serum TRUST, and findings of CSF routine tests including CSF protein concentration and CSF glucose concentration (combined model). The clinical usefulness of the diagnostic models was assessed through the comparison of a receiver operating characteristic (ROC) and decision curve analysis (DCA), which adopted bootstrap resampling 500 times.
Results: A total of 108 patients were analysed (82% males, mean age: 46 years). Of those, 76 were diagnosed as having reactive neurosyphilis under the criteria of positive results in both CSF treponemal and non-treponemal tests. Psychiatric symptoms and serum TRUST were the strongest diagnostic indicators in serum. A diagnostic model was constructed to readily provide the probability of diagnosis at point of care and presented as two nomograms. The basic model reached 79% specificity, 74% sensitivity and 0.82 Area Under the Curves (AUC) (95% CI, 0.72-091), while the combined model showed 82% specificity, 90% sensitivity and 0.88 AUC (95% CI, 0.80-0.94). The integrated discrimination improvement(IDI) index was 0.05 in comparison of two models.
Conclusions: A convenient model using serum TRUST titre and presence of psychiatric symptoms was developed to indicate diagnostic results in patients suspected of NS. Two simple nomograms can be offered to clinicians to facilitate their assessment of patient diagnosis, strengthen the diagnostic decision making, enhance patient stratification, and inform patients in the clinic.
Trial registration: This research was retrospectively registered in Ethics committee on biomedical research, West China Hospital of Sichuan University.