Accuracy of diagnosis of pediculosis capitis: visual inspection vs wet combing.

OBJECTIVE

To determine the diagnostic accuracy of visual inspection and wet combing in pediculosis capitis (head lice infestation). Visual inspection of 5 predilection sites (temples, behind the ears, and neck) was performed first, followed by wet combing of hair moistened with conditioner. Presence of mobile stages was defined as active infestation, presence of nits alone as historic infestation.

DESIGN

Observer-blinded comparison of 2 diagnostic methods.

SETTING

Five primary schools in which head lice infestation was epidemic.

PARTICIPANTS

A total of 304 students aged 6 to 12 years.

MAIN OUTCOME MEASURES: Presence of nymph, adults, and nits; sensitivity, predictive value, and accuracy of both methods.

RESULTS

Visual inspection underestimated the true prevalence of active infestation by a factor of 3.5. The sensitivity of wet combing in diagnosing active infestation was significantly higher than of visual inspection (90.5% vs 28.6%; P < .001). The accuracy of the former method was 99.3% and that of the latter method, 95%. In contrast, visual inspection had a higher sensitivity for the diagnosis of historic infestation (86.1% vs 68.4%; P < .001).

CONCLUSIONS

Wet combing is a very accurate method to diagnose active head lice infestation. Visual inspection is the method of choice, if one aims to determine the frequency of carriers of eggs or nits.