Subgroup analyses based on quality were not informative because of homogenous results and relatively few studies contributing to each comparison.
The largest study contributing to this subgroup analysis is worthy of individual consideration [ 8].
For trials that had multiple arms contributing to different subgroups, the control group was subdivided into two groups to avoid a unit of analysis error.
The arrays containing samples from all the schizophrenic patients was represented by the sum of all four design variables, each multiplied by the fraction of individual contributing to the specific subgroups.
Additionally, the precision of TTE was not homogeneous and depended on patient subgroups with lower precision, particularly in the PREM subgroup, contributing to higher bias and MPE in that subgroup.
Two of the included studies used very similar populations based on a surveillance program with data collection over the same period of time [ 48, 55]; however, both were included in the analyses as they contributed to different subgroup categories, therefore there was insufficient evidence to ascertain whether they were mutually exclusive.
A positive association was seen between elevated serum IL-6 concentrations and sPTB in a meta-analysis (OR = 1.5, 95% CI: 0.7, 3.0) [ 28]; however, this imprecise finding must be interpreted with caution because only two studies contributed to the subgroup analysis.
The factors contributing to heterogeneity were analysed by subgroup analysis, meta-regression or sensitivity analysis by a sequential omission of each individual study.
In a sophisticated analysis examining various factors contributing to epidemiological differences among human subgroups and rates of prostate cancer, Alvarado (this issue) notes that high levels of nutrition in modern Western cultures increases both investment in mate competition and testosterone levels.
With regard to NDNS data, the sample size contributed to uncertainty around subgroup estimates in the statistical models and limited our capacity to examine other population patterns.
