Obstructive sleep apnea and the effect of CPAP treatment on ischemia-modified albumin levels: a multi effect size meta-analysis with diagnostic test accuracy

Purpose: A close association of oxidative stress (OS) and ischemia-modified albumin (IMA) with obstructive sleep apnea (OSA) has been reported in the literature, but the results on IMA are ambiguous. We conducted a meta-analysis to evaluate the association of IMA with OSA and the effect of continuous positive airway pressure (CPAP) therapy on IMA in patients with OSA.

Methods: Relevant studies were identified by searching PubMed and other databases in addition to manual searching of cross-references. Using random-effects model, the standardized mean differences (SMDs), pooled correlation coefficients and summary of diagnostic test accuracies were obtained with 95% confidence intervals (CIs). The meta-regression, sub-group and sensitivity analyses were performed to explore heterogeneity. The presence of publication bias was tested using funnel plot analysis followed by Begg's and Egger's tests for statistical signidicance.

Results: This meta-analysis finally included nine studies. When comparing with non-OSA controls, the OSA patients showed a significantly increased circulatory IMA levels (SMD = 1.15, p = 0.0001). And, this increase is even more pronounced in severe-OSA group as compared to mild-moderate OSA patients (SMD = 076, p = 0.0006). A decrease in post-CPAP treatment IMA was observed when compared with that of baseline values. Meta-analysis of correlations showed significant associations of IMA with polysomnographic parameters. The pooled diagnostic odds ratio and area under curve were 19.58 and 0.888 (Q* = 0.819), respectively. There was no evidence of publication bias for the association of IMA with OSA.

Conclusion: This meta-analysis suggests that OSA is associated with significantly increased IMA levels which may indicate OS, ischemia and subclinical cardiovascular risk. In the diagnostic test accuracy meta-analysis, IMA showed good accuracy for OSA detection. However, further studies are required to establish its clinical utility.