<s>[INST] context: OSAHS is defined on the basis of nocturnal and daytime symptoms as well as sleep study findings. Diagnosis requires the patient to have (1) either symptoms of nocturnal breathing disturbances (snoring, snoing, gasping, or breathing pauses during sleep) or daytime sleepiness or fatigue that occurs despite sufficient oppounities to sleep and is unexplained by other medical problems; and (2) five or more episodes of obstructive apnea or hypopnea per hour of sleep (the apnea-hypopnea index , calculated as the number of episodes divided by the number of hours of sleep) documented during a sleep study. OSAHS also may be diagnosed in the absence of symptoms if the AHI is >15 episodes/h. Each episode of apnea or hypopnea represents a reduction in breathing for at least 10 s and commonly results in a >=3% drop inoxygensaturation and/or a brain coical arousal. OSAHS severity is based on the frequency of breathing disturbances (AHI), the amount of oxyhemoglobin desaturation with respiratory events, the duration of apneas and hypopneas, the degree of sleep fragmentation, and the level of daytime sleepiness or functional impairment. Obstructive Sleep Apnea/Hypopnea Syndrome (OSAHS): Quantification and Severity Scale Apnea-hypopnea index (AHI)a:Number of apneas plus hypopneas per hour of sleep Respiratory disturbance index (RDI):Number of apneas plus hypopneas plus RERAs per hour of sleep Mild OSAHS:AHI of 5-14 events/h Moderate OSAHS:AHI of 15-29 events/h Severe OSAHS:AHI of >=30 events/h aEach level of AHI can be fuher quantified by level of sleepiness and associated hypoxemia. [/INST] question: Apnea- hypopnea index > ______ is used for diagnosis of OSAHS in absence of symptoms? | options: A: 5 episodes/ hr B: 10 episodes/ hr C: 15 episodes/ hr D: 20 episodes/ hr | answer: C </s>