OBJECTIVE: To examine test characteristics of laser Doppler vasomotor reflex testing for leprosy and to determine the prevalence of abnormal responses in leprosy patients, healthy contacts and controls.
DESIGN AND PARTICIPANTS: Cross-sectional study including 89 leprosy patients (mean age 35 years, 74% male), 36 healthy contacts (29 years, 64% male) and 47 controls (30 years, 68% male), for a total of 172 participants.
SETTING: Leprosy hospital in an endemic region 200 km west of Kathmandu, Nepal.
OUTCOME MEASURE: Finger-tip and toe-tip vasomotor reflexes elicited by inspiratory gasp were measured using a laser-doppler flow temperature technique. Results were expressed in per cent as the maximal reduction in bloodflow from baseline.
RESULTS: For all 12 measurement sites there were highly significant (p > 0.0001 to < 0.004) differences between the three groups tested. Leprosy patients consistently had the lowest responses and controls the highest, with healthy contacts showing intermediate values. Thresholds defined as mean bloodflow reductions among controls minus 1.64 or minus 1.96 standard deviations provided optimal combinations of sensitivity and specificity. Using these cut-off values around 80% of leprosy patients, 50% of healthy contacts and 20% of controls had two or more abnormal reflexes (p < 0.0001 for differences between groups).
CONCLUSIONS: In endemic regions, subclinical autonomic neuropathy may be an early but detectable marker for the risk of subsequent leprosy, making early treatment and prevention of transmission possible. Prospective studies are needed to establish the predictive value of abnormal vasomotor reflexes.
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