In total, 517 articles were obtained from 4 databases, among which 295 were from Pubmed, 111 were from Web of Science, 13 were from Cochrane Library, and 98 were from MEDLINE/EMBASE. 84 of the 517 articles were RCTs or cohort studies. Additional 12 articles (RCTs or cohort studies) were extracted from references of previous meta-analyses and their included studies.
All the 96 RCTs or cohort studies were included for screening. Initially, nine articles (six from Web of Science and three from MEDLINE/EMBASE) were found to be duplicated, and were therefore excluded from the 96 articles. After screening titles and abstracts, 43 of the remaining 87 articles were excluded. Subsequently, 25 articles were excluded from the remaining 44 articles after screening the full-text of each study, among which one article was a news report, three articles reported patients with cryptococcal disease, two articles reported HIV-negative patients with cryptococcal antigenemia, four articles reported data from patients with CM or asymptomatic CM, six articles reported data from HIV-infected patients with negative CrAg, one article reported on the epidemiology of cryptococcosis, and eight articles did not report CD4+ T cell counts or primary outcomes. Finally, a total of 19 articles were included in our meta-analysis.
The characteristics of the 19 included studies were shown in Table 1. Our assessment of quality and potential risk bias in these studies indicated that the following factors could contribute to clinical and methodological heterogeneity, including: (1) the confounding factors or subject recruiting or incomplete follow-up in nine of the 18 cohort studies, (2) the unclear risk of attrition in the RCT, and (3) the unclear risk of reporting and other bias in the RCT, as shown in Supplementary Table 1 and Supplementary Table 2.
Fourteen of the 19 included studies reported the prevalence of CrAg positivity (1949 persons with CD4+ T cell counts<200 cells/μL in four studies; 783 persons with CD4+ T cell counts<150 cells/μL in one study; 5984 persons with CD4+ T cell counts<100 cells/μL in nine studies). The pooled CrAg positivity prevalence in 8716 HIV-infected persons with CD4+ T cell counts<200 cells/μL was 6% (95%CI: 4-7, I2=92.0%), as shown in Figure 2.
Fourteen studies reported the incidence of CM among CrAg+ persons (1806 persons with CD4+ T cell counts<200 cells/μL in four studies; 312 persons with CD4+ T cell counts<150 cells/μL in two study; 248 persons with CD4+ T cell counts<100 cells/μL in eight studies), and five studies reported the incidence of CM among CrAg- persons (54 persons with CD4+ T cell counts<200 cells/μL in one studies; 4020 persons with CD4+ T cell counts<100 cells/μL in four studies). The incidence of CM in 2349 CrAg+ persons was 7% (95%CI: 4-10; P=0.000; I2=72.8%), whereas the incidence of CM in 4074 CrAg- persons was 0% (95%CI: 0-1; P=0.071; I2=53.6%), as shown in Table 2 and Supplementary Figure 1a.
Eleven studies reported the incidence of CM among persons who received antifungal therapy (922 persons with CD4+ T cell counts<200 cells/μL in four studies; 166 persons with CD4+ T cell counts<150 cells/μL in two studies; 240 persons with CD4+ T cell counts<100 cells/μL in five studies), and nine studies reported the incidence of CM among persons who received placebo or no intervention (946 persons with CD4+ T cell counts<200 cells/μL in three studies; 146 persons with CD4+ T cell counts<150 cells/μL in one study; 160 persons with CD4+ T cell counts<100 cells/μL in five studies). The incidence of CM of 1163 persons receiving antifungal therapy was 3% (95%CI: 1-5; P=0.000; I2=70.5%), whereas the incidence of CM of 1252 persons in nine studies who received placebo or no intervention was 9%, which equates to a 67% reduction in CM incidence in persons receiving antifungal therapy (95%CI: 5-13; P=0.000; I2=73.7%), as shown in Table 2 and Supplementary Figure 1b.
Five studies compared the incidence of CM between 1094 persons receiving azoles and 1076 persons receiving placebo or no intervention (1785 persons with CD4+ T cell counts<200 cells/μL in three studies; 295 persons with CD4+ T cell counts<150 cells/μL in one study; 90 persons with CD4+ T cell counts<100 cells/μL in one study). We found that the risk ratio of CM events among persons who received placebo or no intervention was 5.51 times higher than that of those who received antifungal therapy (95%CI: 2.60-11.67; P<0.00001; I2=15%), as shown in Figure 3.
Fourteen studies reported all-cause mortality among CrAg+ persons (1953 persons with CD4+ T cell counts<200 cells/μL in six studies; 312 persons with CD<150 cells/μL in two studies; 255 persons with CD4+ T cell counts<100 cells/μL in six studies), seven studies reported all-cause mortality in CrAg- persons (54 persons with CD4+ T cell counts<200 cells/μL in one study; 4000 persons with CD4+ T cell counts<100 cells/μL in six studies). The all-cause mortality of 2520 CrAg+ persons was 18% (95%CI: 11-25; P=0.000; I2=93.6%), 1.06 times that of 4054 CrAg- persons (17%, 95%CI: 7-27; P=0.000; I2=98.8%), as shown in Table 2 and Supplementary Figure 2a.
Ten studies reported all-cause mortality in persons who received antifungal therapy (230 persons with CD4+ T cell counts<200 cells/μL in four studies; 166 persons with CD4+ T cell counts<150 cells/μ in two studies; 240 persons with CD4+ T cell counts<100 cells/μL in four studies), seven studies reported all-cause mortality in persons receiving placebo or no intervention (946 persons with CD4+ T cell counts<200 cells/μL in three studies; 146 persons with CD4+ T cell counts<150 cells/μL in one study; 110 persons with CD4+ T cell counts<100 cells/μL in three studies). The all-cause mortality of 636 persons receiving antifungal therapy was 17% (95%CI: 11-22; P=0.000; I2=69.5%), which was similar to that of 1202 CrAg- persons receiving placebo or no intervention (16%, 95%CI: 7-24; P=0.000; I2=92.4%). Details are shown in Table 2 and Supplementary Figure 2b.
Five studies (1897 persons with CD4+ T cell counts<200 cells/μL in three studies; 295 persons with CD4+ T cell counts<150 cells/μL in one study; 90 persons with CD4+ T cell counts<100 cells/μL in one study) compared all-cause mortality between persons who received azole antifungal therapy and persons who received placebo or no intervention. No significant difference was found in all-cause mortality (risk ratio: 0.82, 95%CI: 0.42-1.60; P=0.04; I2=61%) between 1138 CrAg+ persons who received an azole drug and 1144 CrAg+ persons who received placebo or no intervention (Figure 4).
In addition, we estimated and compared the prevalence of CrAg positivity, the incidence of CM and all-cause mortality between persons with CD4+ T cell counts<100 and persons with CD4+ T cell counts between 100-200 cells/μL. The results showed that the risk ratio of CrAg positivity prevalence among HIV-infected persons with CD4+ T cell counts<100 cells/μL was1.82 times that of those with 100-200 cells/μL (95%CI: 0.77-4.30; p=0.007, I2=63%; three studies; 1886 persons). The risk ratio of the incidence of CM among HIV-infected persons with CD4+ T cell counts<100 cells/μL was 2.53 times that of those with CD4+ T cell counts between 100-200 cells/μL (95%CI: 0.50-12.71, p=0.26, I2=59%; four studies, 1960 persons). The risk ratio of the all-cause mortality among HIV-infected persons with CD4+ T cell counts <100 cells/μL was 4.15 times that of those with CD4+ T cell counts between 100-200 cells/μL (95%CI: 0.89-19.42, p=0.07, I2=0%; two studies, 1552 persons) . Further, the risk ratio of the incidence of CM among persons with CD4+ T cell counts between 100-200 cells/μL receiving placebo or no intervention was 1.15 times compared to those receiving antifungal treatment (95%CI: 0.16-8.13, p=0.97, I2=0%; three studies; 140 persons) . The risk ratio of the all-cause mortality among persons with CD4+ T cell counts between 100-200 cells/μL receiving antifungal treatment was 0.27 compared to those receiving placebo or no intervention (95%CI: 0.01-4.93, p and I2 not applicable; one study; seven persons). Details are shown in Table 3.