ObjectiveTo investigate the diagnostic value of oximetry in sleep apnea hypopnea syndrome (SAHS). MethodsAdult patients suspected for SAHS were enrolled between May 2010 and May 2013. The patients underwent both polysomnography (PSG) and oximetry for further diagnosis. Apnea hyponea index (AHI) and oxygen desaturation index four (ODI4) were calculated on a single night. The relationship between AHI and ODI4 were analyzed. ResultsA total of 628 adult patients were recruited.ODI4 was linearly correlated with AHI with a regression coefficient of almost 1. The cut-off values of ODI4 for indentifing SAHS and moderate to severe SAHS were 10 events per hour and 20 events per hour, with specificities of 99.9% and 99.3%, and AUCs of 0.931 and 0.934, respectively. Female, lower weight and less severe SAHS patients were easily misdiagnosed. ConclusionsThere is a high agreement between AHI and ODI4. Oximetry is less likely misdiagnose SAHS.