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

Abstract

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. 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. 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. 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. 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.