PURPOSE: Various predictive models to screen Obstructive sleep apnea (OSA) have been tried. Modified Friedman score (MFS) is a good correlate of presence and severity of OSA in a unselected population. However, the prevalence and validity of MFS in a subgroup of non-obese patients with OSA is not well established. The aim of our study is to address the utility of MFS in non obese patients with OSA.
METHODS: A retrospective study was conducted. Patients with a BMI < 30 referred to our sleep lab were included. All patients had overnight polysomnography. Upper airway assessment and MFS was recorded. Patients were diagnosed with OSA using a threshold value of RDI >10.
RESULTS: A total of 123 patients with OSA (83 males and 40 females) and 123 subjects (63 males and 60 females) without OSA (control) were included. Patients with OSA were older (62.7± 13.9 vs. 55 ± 15.3 p0.002) and had higher BMI (27.3 ± 2.2 vs. 26.1 ± 3.1 p 0.0005) than the control group. Marked difference in percentage of abnormal MFS between the OSA and the control group (48.7% vs. 29.2% p 0.002) is noticed. The difference in percentage of abnormal MFS (between the OSA and control group) is more pronounced in women (50% vs. 26.6% p0.02) than men (48.2% vs. 31.7% p0.06 respectively). Overall MFS's sensitivity specificity, positive predictive value (PPV) and negative predictive value were 48.7%, 70.7%, 62.5% and 58% respectively for OSA in this cohort of non-obese patients.
CONCLUSION: Even in non-obese patients, MFS has a high PPV for OSA. Nearly half of non-obese patients with OSA have an abnormal upper airway. There are gender influences noted with women having a higher percentage of abnormal MFS in OSA group.
CLINICAL IMPLICATIONS: Screening strategies for patients should include a simple assessment of upper airway dimensions. This may prove to be useful particularly in patients where a suspicion of sleep apnea may not be entertained on account of absence of obesity.
DISCLOSURE: Gnananandh Jayaraman, No Financial Disclosure Information; No Product/Research Disclosure Information