Polygraphy vs. polysomnography: missing osas in symptomatic snorers—a reminder for clinicians

Purposes The purposes of this study are to investigate the usefulness of polygraphy (PG) in diagnosing obstructive sleep apnea (OSA) in sleepy/tired snorers compared to polysomnography (PSG) and, further, to search for suspected respiratory arousals in the PG. Methods One hundred eighty-seven adults suffering from sleepiness/tiredness and snoring had undergone ambulant PG and were considered to be normal, using American Academy of Sleep Medicine’s 2007 hypopnea criteria A. After approximately 7 months, in-lab PSG was performed using hypopnea criteria B, where arousals are also recognized. Validated questionnaires (Hospital Anxiety and Depression Scale, self-rated general health) were answered. In a subgroup, the sensitivity and specificity were calculated for flow limitation index (FLI) and flattening index (FlatI) in PG compared with the respiratory distress index (RDI) in PSG. Results Despite the normal PG, at PSG, the median RDI was 11.0 (range, 0–89.1). One hundred sixty-eight out of one hundred seventy-eight (90 %) were found to have at least mild OSA and 119/187 (64 %) with moderate–severe OSA according to the RDI values. The sensitivity and specificity were low (