Serum cryptococcal antigen titre as a diagnostic tool and a predictor of mortality in HIV-infected patients with cryptococcal meningitis.

OBJECTIVES: The aim was to determine the effectiveness of the serum cryptococcal antigen (CrAg) test in the diagnosis of concurrent cryptococcal meningitis (CM) and as a predictor of mortality in HIV-infected patients.

METHODS: In this retrospective study, all HIV-infected patients admitted to Shanghai Public Health Clinical Center from 1 January 2014 to 31 August 2016 were screened for serum CrAg using the latex agglutination test. Serum CrAg-positive patients underwent lumbar puncture to confirm CM prior to the initiation of appropriate antifungal therapy and were followed up for at least 6 months.

RESULTS: One hundred and four (7.1%) of the total of 1474 HIV-infected patients screened were serum CrAg-positive. CM was diagnosed in the majority of serum CrAg-positive patients (71.3%; 67 of 94) and was confirmed in all (46 of 46) of the patients with headache or coma and in 43.8% (21 of 48) of patients without neurological symptoms. CrAg titres ≥ 1:1024 showed a sensitivity of 82.5% and a specificity of 86.7% for the diagnosis of concurrent CM (P < 0.001). The positive predictive value for CM in this population was 94.3%. A total of 13 serum CrAg-positive patients [13.8%; 95% confidence interval (CI) 7.5-22.4%] died (11 as a result of CM and two others as a result of bacterial pneumonia) despite early antifungal treatment initiation. Serum CrAg titres ≥ 1:1024 predicted all-cause mortality (hazard ratio 3.69; P = 0.03).

CONCLUSIONS: Serum CrAg titres ≥ 1:1024 not only were associated with concurrent CM but also predicted mortality. HIV-infected patients with a positive serum CrAg test during screening should receive lumbar punctures regardless of symptoms to rule out CM and patients with serum CrAg titres ≥ 1:1024 should be offered immediate care.