Pre-polysomnographic assessment using the Pittsburgh Sleep Quality Index questionnaire is not useful in identifying people at higher risk for obstructive sleep apnea

Background: Polysomnography remains the diagnostic gold standard for obstructive sleep apnea syndrome (OSAS), but it is time consuming and requires dedicated personnel and setting. It may be more useful to plan a polysomnogram based on a preliminary screening. Objective: To verify whether a questionnaire of general quality of sleep, the Pittsburgh Sleep Quality Index (PSQI), could outperform a dedicated questionnaire (Epworth Sleep Scale: ESS) in targeting OSAS patients in an at risk population. Methods: 254 consecutive subjects attending the outpatient clinic for respiratory diseases were clinically evaluated for sleep apnea and referred to a 12 channel night-time polysomnography. All patients were administered the ESS and the PSQI before the procedure. The correlation between the Apnoea/Hypopnoea Index (AHI) and the global score of the PSQI was calculated; Sensitivity, specificity, positive and negative predictive values (PPV and NPV, respectively), Diagnostic accuracy and the area under the receiver operating characteristic curve (AUC) were calculated. ESS performance was used as a control reference. Results: The mean age was 65.8 (standard deviation: 12.1) and the study group was 68.4% male. The mean BMI was 38.5; SD 7.7. Prevalence of OSAS in the study population was 55.5%; OSAS was severe in 60.5% of OSAS patients. ESS was significantly, but weakly, correlated with the AHI (AHI vs ESS: R = 0.308; p < 0.001), whereas PSQI was not (R = 0.037; p = 0.581). Both PSQI and ESS, however, performed unsatisfactorily: sensitivity 37.8% and 69.7%; Specificity 76.1% and 31.0%; Diagnostic Accuracy 57.5% and 49.8%; PPV 60% and 48.7%; NPV 56.3% and 52.2%; AUC 0.589 and 0.509, respectively. Conclusions: The PSQI score is not helpful in the pre-polysomnographic assessment of people with suspected OSAS. Further studies are required to provide reliable pre-clinical instruments targeting patients amenable to polysomnography.