Abstract: 【Abstract】 Objective To investigate the value of serum prealbumin in indicating asymptomatic neurosyphilis among patients with serofast syphilis. Methods This was a case-control study. A total of 75 serofast syphilis inpatients with suspected asymptomatic neurosyphilis were enrolled at the Fifth People's Hospital of Suzhou from June 2018 to February 2024. Based on the confirmed diagnosis, they were divided into an asymptomatic neurosyphilis group （25 cases） and a non-neurosyphilis group （50 cases）. During the same period, 50 inpatients with symptomatic neurosyphilis and 125 healthy physical examinees were selected. The serum prealbumin levels and lymphocyte subset counts of the patients at the initial visit and those of the healthy controls were retrospectively reviewed. Logistic regression analysis was performed on the prealbumin levels of patients with serofast syphilis, and receiver operating characteristic （ROC） curves were plotted to evaluate the value of serum prealbumin levels in indicating asymptomatic neurosyphilis among patients with serofast syphilis. Thirty-five inpatients with serofast syphilis and suspected asymptomatic neurosyphilis were enrolled at the Fifth People's Hospital of Suzhou between June and December 2025 as a validation set to assess the value of serum prealbumin as an indicator of asymptomatic neurosyphilis. Results In the asymptomatic neurosyphilis group, there were 14 males and 11 females, aged 21.0 to 70.0 years; in the symptomatic neurosyphilis group, there were 28 males and 22 females, aged 21.0 to 78.0 years; in the non-neurosyphilis group, there were 28 males and 22 females, aged 22.0 to 76.0 years; in the healthy control group, there were 70 males and 55 females, aged 25.0 to 76.0 years. The serum prealbumin level was significantly higher in the asymptomatic neurosyphilis group （M ［Q1, Q3］: 267.00 ［235.00, 319.00］ mg/L） than in the non-neurosyphilis group （224.0 ［196.00, 281.75］ mg/L, P < 0.05） and the healthy control group （236.00 ［218.50, 274.00］ mg/L, P < 0.05）, but there was no significant difference between the asymptomatic neurosyphilis group and the symptomatic neurosyphilis group （257.0 ［218.98, 300.25］ mg/L; Z = 1.16, P > 0.999）. Multivariate logistic regression analysis showed that the risk of asymptomatic neurosyphilis in patients with serofast syphilis increased with increasing prealbumin levels （OR ［95% CI］: 1.021 ［1.007, 1.034］）. The ROC curve showed that the area under the curve of serum prealbumin for predicting asymptomatic neurosyphilis was 0.693 （95% CI: 0.571 - 0.815）, with a cut-off value of 226.50 mg/L, a specificity of 88%, and a sensitivity of 52%. In the validation set, the serum prealbumin level was significantly higher in patients with asymptomatic neurosyphilis （10 cases; 279.26 ± 15.57 mg/L） than in non-neurosyphilis patients （25 cases; 242.24 ± 9.20 mg/L, t = 2.11, P = 0.043）; 9 of 10 patients with asymptomatic neurosyphilis had a serum prealbumin level > 226.50 mg/L, and 15 of 25 non-neurosyphilis patients had a serum prealbumin level > 226.50 mg/L; at this cut-off value, serum prealbumin had a sensitivity of 90% and a specificity of 40% for indicating asymptomatic neurosyphilis. Conclusion Serum prealbumin has a certain indicative value for asymptomatic neurosyphilis among patients with serofast syphilis.

Key words: Neurosyphilis, Serum prealbumin, Serofast syphilis, Asymptomatic neurosyphilis, Risk assessment