The Effect of Educational Intervention on Ecacy of 1% Permethrin Shampoo and 4% Dimeticone Lotion to Treat Head Lice Infestation Using Propensity Score Matching (PSM)

Background Head lice are a main public health problem and the most important human ectoparasites and the use of pediculicides is the most common way to control it. One of the possible causes of treatment failure is the lack of improper application of pediculicide. The aim of this study was to assess the effect of education on ecacy of 1% permethrin or 4% dimeticone lotion to treat head lice infestation. This quasi-experimental study was performed on 100 people infected with head lice in comprehensive urban health centers of Ardabil (intervention group) and 400 people of East Azerbaijan and West Azerbaijan (control group) provinces from April to March 2019. The data collection tool included demographic questionnaire and examination evidence recording sheet in terms of presence of hits or adult lice. The outcome of treatment included elimination of head lice infestation on days 7, and in the case of recurrence, it was considered on days 14 and 30 after treatment. Data were analyzed using R software and Generalized Estimating Equation method. GEE analysis showed there is signicant difference in evaluating head lice over time. of Health, was done on 100 subjects with head lice infestation in comprehensive urban health centers of Ardabil province (intervention group) and 400 subjects of East Azerbaijan and West Azerbaijan (control group) provinces from April to March 2019. The two provinces of Azerbaijan and Ardabil, from which case and control samples have been selected, are completely similar in terms of culture, customs, lifestyle, economic and social status. The number of subjects for each treatment method in all urban and rural areas was equal, so the equal distribution of socio-economic confounding factors in response to treatment was ensured. The most important confounding factor in therapeutic effect was the possibility of re-infestation of people who are around the infected person after the start of the trial and treatment, which could potentially appear in the role of reducing the therapeutic effect. To overcome it, all home contact cases, without considering that infestation was diagnosable or non-diagnosable, were treated simultaneously.


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In the intervention group, before prescribing the shampoos, the correct method of using these anti-lice shampoos was practically taught by the medical entomology experts. Subjects in intervention group received 30 minutes of training. The training consisted of the head lice and ways of transmitting the disease (10 minutes), the pediculicide such as 1% permethrin and 4% dimeticone lotion (10 minutes) and how to use them properly in the treatment of head lice (10 minutes) using role-playing method. However, the control group in both East and West Azerbaijan provinces were treated routinely. Each treatment included using 1% permethrin shampoo twice or 4% dimethicone lotion according to the instructions. The outcome of the treatment included removal of adult human head lice, nymphs, and nits in con rmed human cases at 14 and 30 days after starting treatments were considered. Data were collected through a researcher-made questionnaire and through observation and examination.

Data analysis
Unlike clinical trial studies, in observational studies subjects are not assigned at random to two groups and estimation the effect of treatment would have been challenging [11]. Random assignment is done in order to distribution of covariate in both group become similar and in this sense groups are comparable. The propensity score matching (PSM) is a powerful method, in situation that random assignment is absent, for balancing numerous observed covariates [12].
In this study by using PSM confounding variables and treatment selection were controlled. Based on PSM multidimensional pretreatment confounder covariates transformed to one-dimensional variable and as a result similarity in distribution of covariates in both groups is happened [13]. Next the propensity score was calculated, and matching was done. All 100 patients in case group were matched by applying by1:2 PSM employing nearest neighbor method.
Prognostic score based balanced was used in order to evaluating bias reduction in PSM. The most popular matric balance measure prognostic score, standardized mean difference (SMD), has been used. This statistics is used to examine the balance of confounders between intervention and control group [14]. SMD greater than 0.1 shows the signi cant dissimilarity [15]. The strength of SMD is sample size does not have in uence on it [16]. Figure 1 shows study follow diagram. In the next step matched data, since head lice infestation each individual was investigated three times and measurements are dependent, for considering dependency, generalized Estimating Equations (GEE) was applied [17]. All statistical analysis were done using R version 3.6.3 software.

Result
In total, 100 subjects in intervention group and 400 subjects in control group completed the study. The result showed before applying PSM the mean age of intervention and control group was signi cantly different. The age of individual in intervention group was 16.18±12.61 and in control group it was 13.09±10.21(P<0.05) and SMD for age of participants 0.27 was obtained. Conspicuously SMD showed the distribution of age is too different to compare, while after applying PSM the age of individuals in both group was not statistically signi cant any more (16.18±12.61 vs 16.34 ±12.52 in intervention and control groups respectively, P-value=0.92). The comparison of characteristics of both group before and after applying PSM are presented in table1. This

Discussion
The use of insecticides with different formulations of lotions and shampoos is the most common method of controlling head lice and treatment of pediculosis. Sometimes, pediculicides are not effective and in some cases there is a possibility of recurrence. One of the possible causes of failure in treatment is the lack of awareness and proper use of pediculicides. Based on the results of the present study, the educational intervention showed a signi cant difference in the test group, but in the control group, this difference was not signi cant. In other words, teaching the way of using pediculicides properly and health tips were effective in treating and reducing recurrence. Several studies have been conducted in the treatment of head lice infestation [18][19]. Most studies have compared different treatments [19][20][21], and several studies have been conducted on the effectiveness of training programs on preventing pediculosis capitis [22][23]. No study was found to investigate the effect of training on the e cacy of pediculicides in the treatment of head lice. In a study conducted by Zareban, the health education program had a positive effect on reducing head lice infestation, and after educational intervention, the rate of infestation in the experimental group decreased by 17.6%%, but it did not difference in the control group [24]. In the study conducted by Chegini (2017), mothers received group discussion on the preventive behaviors of pediculosis and it led to a reduction in the incidence of pediculosis in their daughters [23]. However, in the study conducted by Eftekhari (2017), educational intervention is effective in promoting preventive behaviors against pediculosis on female elementary school students [22]. In general, the results of research con rmed the effectiveness of education in reducing the recurrence of head lice infestation in the study subjects. People knowledge of the way of properly use of pediculicides can signi cantly reduce the rate of head lice infestation. This issue should be considered by health care providers.