Decreased blood natural killer cells in serofast patients: a systematic review and meta-analysis

Currently, increasing attention has been paid to the association of the serofast status with natural killer (NK) cells. Remarkable diversity among the results of different studies has been observed. We conducted this meta-analysis to evaluate the variation of the proportion of NK cells in serofast patients compared with that of healthy controls and cured patients. Through the designed retrieval methods, 631 serofast patients, 562 healthy controls and 160 patients whose serology turned negative following treatment were derived from 16 publications for further analysis. The established items were used for the standard selection and quality assessment. The Stata software was used for meta-analysis. The final results indicated that serofast patients exhibited a dramatic decrease in the number of NK cells in the peripheral blood compared with that noted in healthy control subjects [standardized mean difference (SMD) = -0.63, 95% CI (-1.08, -0.17), p = 0.007]. The proportion of NK cells was significantly lower in serofast patients than that noted in cured patients [SMD = -0.25, 95% CI (-0.48, -0.02), p = 0.033] and no significant difference was noted in the proportion of NK cells between cured patients and healthy controls [SMD = -0.39, 95% CI (-0.93, 0.14), p = 0.148]. The present meta-analysis indicated that the proportion of NK cells in the peripheral blood was significantly lower in serofast patients compared with that of the healthy controls and cured patients, indicating that the reduction in the number of NK cells may be closely associated with the syphilis serofast status.