Aim: The aim of our study was to evaluate the sensitivity and specificity of Nocturnal Oximetry (NO) as a diagnostic screening tool for obstructive sleep apnoea hypopnoea syndrome (OSAHS), compared with polysomnography (PSG) as the gold standard.
Methodology: 63 patients with clinical suspicion of OSAHS and exclusion of respiratory disease underwent PSG and NO. We then determined NO sensitivity, specificity, positive (PPV) and negative predictive values (NPV).
Results: OSAHS was diagnosed in 47 patients with a mean age of 54 years. In the evaluation of the percentage of Total Sleep Time (TST) with oxygen desaturation below 90%, we found significant differences between patients with OSAHS (25.4 +/- 29.7%) and without OSAHS (1 +/- 1.5%), p< 0,001. We used two cutoff points to evaluate sensitivity, specificity, positive (PPV) and negative predictive values (NPV), based on the severity of O2 desaturation (StO < 90%). Using the first cutoff point we 2 diagnosed with NO as positive all the patients with TST desaturation values =1% of the TST. Under these circumstances we found a sensitivity of 76.6%, a specificity of 75%, a PPV of 90% and an NPV value of 52.2% for our screening test (NO). Using the second cutoff point, we diagnosed with NO as positive all the patients with TST desaturation values =5% of the TST. With this method we found a sensitivity of 65.9%, a specificity of 100%, a PPV of 100% and an NPV of 50%.
Conclusion: NO is a useful screening test for the diagnosis of OSAHS in patients without respiratory disease.