Make the Diagnosis: Sleep Apnea
Prior Probability of Sleep Apnea
The prevalence of sleep apnea in community-screened patients is 2% to 14% when the diagnosis is established by an apnea-hypopnea index (AHI) ≥ 5/h.1,2 and 3
Patients in Whom Sleep Apnea Should Be Considered
Patients with sleep apnea tend to be older patients with a high body mass index (BMI). Family members may report that the patient has habitual, loud, disruptive snoring that can also be associated with choking or gasping and actual episodes of apnea. The patient may recognize none of those symptoms, but he or she may frequently complain of fatigue. Daytime sleepiness is more important than fatigue, and is characterized by situations in which the patient would be expected to exhibit alertness but instead feels sleepy. Fatigue is a generalized sense of weariness.
Assessing the Likelihood of Sleep Apnea
Snoring is common in the general population, so as an isolated symptom it has little effect on the likelihood of sleep apnea (positive likelihood ratio [LR], 1.3-1.5). Nocturnal gasping or choking is the only symptom that by itself has an LR+ > 2.0 (see Table 92-1). The absence of apneas is the most useful finding for identifying patients without sleep apnea.
Table 92-1.Accuracy of Findings for Sleep Apnea |Favorite Table|Download (.pdf) Table 92-1. Accuracy of Findings for Sleep Apnea
|Symptoms ||AHI Threshold ||LR+ (95% CI) ||LR- (95% CI) |
|Nocturnal choking/gasping ||≥ 10 or ≥ 15 ||3.3 (2.1-4.6) ||0.57 (0.38-0.76) |
|Reported apneas ||≥ 10 or ≥ 15 ||1.4 (1.2-1.5) ||0.47 (0.38-0.56) |
|Combinations of Findings |
|Snoring severity scale ≥ 4a and body mass index > 26 ||≥ 15 ||1.3 (1.3-2.0) ||0.07 (0.03-0.19) |
Because most individual symptoms or signs lack diagnostic accuracy, physicians usually evaluate patients for combinations of findings. Unfortunately, the physician’s overall impression is not more useful than the individual symptoms or signs (overall clinical impression of sleep apnea: LR+, 1.7; 95% CI, 1.5-2.0; LR- 0.67; 95% CI, 0.60-0.74). The Snoring Severity Scale4 in combination with BMI is most useful for ruling out the likelihood of moderate to severe sleep apnea, but it requires confirmation in additional studies that also assess its accuracy for mild sleep apnea (AHI, 5 to < 15). The Sleep Apnea Clinical Score5 combines the results of 4 findings (snoring, nocturnal gasping or choking, hypertension, and neck circumference) and then uses a grid to determine the score. Like the Snoring Severity Scale, it has been evaluated in only 1 study. However, the Sleep Apnea Clinical Score may be the most useful combination for identifying patients most likely to have sleep apnea (see Table 92-2...