Crocker et al developed a screening equation based on clinical findings to predict the probability of an abnormal Apnea-Hypopnea Index (AHI) during a sleep study. This can help select patients at greater need for sleep studies and to reduce negative tests. The authors are from the Royal Newcastle Hospital in Australia.
Parameters:
(1) age in years
(2) presence of apneic episodes during sleep
(3) body mass index (BMI) in kilograms per square meter
(4) history of hypertension
Parameter
Finding
Points
apnea observed during sleep
absent
0
present
1
history of hypertension
absent
0
present
1
X =
= (0.06 * (age in years)) + (2.98 * (points for sleep apnea)) + (0.23 * (BMI)) + (1.35 * (points for hypertension)) – 13.9
estimated probability of AHI index > 15 =
= 1 / (1 + EXP((-1) * X))
Interpretation:
• A probability of >= 0.15 (15%) was considered "positive" for an AHI > 15.
Performance in study groups:
• Sensitivity 92%, specificity 51%
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