The role of nocturnal oximetry in obstructive sleep apnoea-hypopnoea syndrome screening.

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.