Utility of Serum Markers in Obstructive Sleep Apnoea Syndrome: A Case-control Study

Introduction: Obstructive Sleep Apnoea Syndrome (OSAS) consists of cessation of breathing for at least 10 seconds during sleep in spite of inspiratory efforts. The OSAS is an independent risk factor for a number of cardiovascular diseases and cerebrovascular events. The OSAS is diagnosed and assessed by polysomnography which is time consuming and expensive. C-Reactive Protein (CRP) and Creatine Phosphokinase (CPK) are markers of systemic inflammation. Inflammatory component is present in OSA. Biomarkers like CRP and CPK may serve as diagnostic tools which are simpler, cheaper and quicker alternatives. Aim: To study the role of serum markers CRP and CPK in the diagnosis of sleep disordered breathing. Materials and Methods: This was a case-control study, conducted from May 2021 to October 2021, in the Department of Pulmonary Medicine, NRI Medical College, Guntur, Andhra Pradesh, India. Total 50 patients were studied for their various symptoms suggestive of OSAS and confirmed by polysomnography were selected for the study. Total 40 age and weight matched controls were included in the study. The association of serum CRP and CPK with OSA was assessed. The Z-test of difference between two proportions was used to compare gender and smoking status of study participants of the two groups. The p-value < 0.05 was reported as statistically significant. Results: The mean CRP in those suffering from obstructive sleep apnoea was 12.075 +/- 7 mg/dL with 13.89 in moderate to severe OSAS group and 10.26 in mild cases. The CRP showed statistically significant association (p-value=0.00344) with OSA whereas CPK levels in OSA subjects showed no statistically significant association with OSAS. Sensitivity of CRP and CPK compared to the Apnoea Hypopnea Index (AHI) in the diagnosis of OSAS was 66% and 34%, respectively. Specificity of CRP and CPK was 87.5% for both. Positive predictive value for CRP and CPK was 86.8% and 77.2%, respectively. Conclusion: C-reactive protein, a systemic inflammatory marker has a potential role in the diagnosis of OSAS.