To the Editor: For parents to treat head lice (pediculosis) effectively in their children, it is necessary for them first to recognise it is present. We conducted a school-based screening program involving 1838 children from 16 randomly selected primary schools in Victoria between May and October 2001 (participation rate, 55.2%).1 As part of this program, we compared a written report from parents on their child’s pediculosis status against results of our examination (7–10 days later).

We examined the scalp and hair of each child for lice (“crawlers”) or viable louse eggs (“active infestation”) and dead or hatched louse eggs (“inactive infestation”) using white hair conditioner, which makes lice and eggs easier to see with the naked eye, and a fine-toothed head lice comb. This is a validated, accurate and sensitive diagnostic technique.2 Parents were unaware of the proposed screening date, and the study team was unaware of the parents’ reports.

We compared parental report about pediculosis against results of our screening for 1179 children who could be matched with completed questionnaires. Overall, 149 children (12.6%) had active pediculosis, but parents reported head lice in only 36 children (3.0%) (Box 1 and Box 2). These comprised 24 of the 149 children with confirmed pediculosis (16%), and another 12 children who did not have pediculosis when examined. The positive predictive value (PPV) of parental report was 66.6%, indicating that parental reporting was not a reliable indicator of pediculosis. An implication of the low PPV is that some children may have been unnecessarily treated with insecticide for an infestation they did not have.

On the other hand, a substantial proportion of children with head lice had not been identified by their parents and could contribute to ongoing transmission within schools. While it was possible they were infected subsequent to completion of the questionnaire, this seemed unlikely, as 72% were found to have multiple louse eggs, indicating a longer duration of infestation than the 7–10 days since the questionnaire was completed.

Our study clearly demonstrates that parental reporting of head lice in their children is unreliable. We suggest several possible reasons: parents did not see the head lice, did not recognise them, or used a diagnostic technique with a lower sensitivity than the method we chose, such as examining dry hair. It is also possible that parents were inhibited from reporting pediculosis by the possible repercussions, such as exclusion of the child from school. Indeed, children whose parents failed to answer the question about pediculosis had a higher prevalence of head lice than those whose parents answered. Nevertheless, parents’ management of pediculosis is likely to improve if a sensitive detection method is used. To improve the sensitivity of parental diagnosis and control of head lice we recommend that parents be instructed to screen their children weekly using hair conditioner and combing.