The biological validity and feasibility of the community based questionnaire approach in determining the epidemiological status of disease and insect vector nuisance

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In the present study, the community-based questionnaire approach using an existing disease surveillance network and the school system was compared and validated with standardized biomedical and other techniques for guineaworm infection, schistosomiasis morbidity and blackfly nuisance monitoring. In all, 707 community key informants and 6,020 children were interviewed in 194 communities (70 with schools and 124 without schools) in East Mamprusi District of the Northern Region of Ghana. The communities/schools were randomly allocated to be interviewed during the rainy season or dry season. Children in ninety-nine communities were interviewed in the rainy season and those in the remaining ninety-five communities interviewed in the dry season. All questionnaires were returned within four weeks. Reagent strip tests for haematuria, urine filtration and microscopy were used for validating schistosomiasis, whilst re-interviews by research team for consistency and checks on evidence of infection were used to validate guineaworm and indirect validation for blackfly nuisance was done with checks on the probability of occurrence of the flies at the time of the survey, using Atlas GIS computer software. The sensitivity, specificity, and predictive values of questionnaires in identifying guineaworm were very high. The kappa statistic (K) was very high (0.92), indicating almost complete agreement between questionnaire responses and guineaworm validation. The prevalence of guineaworm of 1.2% from questionnaires is in line with previous epidemiological findings of guineaworm infection in the study area. In this study, the 3+ positives of the investigators’ and interviewers’ reagent strip testing indicated good agreement (K 083 and 0.77 respectively) with microscopy and is therefore a better indicator of positive status of schistosomiasis in the study area. The validity of the questionnaires was less than satisfactory, with very low sensitivity and positive predictive value (4.2%) and very poor agreement with microscopy (K = 0.07). The specificity and negative predictive value were high as generally expected in low prevalence areas. The low prevalence of schistosomiasis in the study area (<1%) complements the key informants’ low ranking for ‘blood in urine’. Questionnaires were fairly sensitive and specific in a high prevalence school (Buipe) but not in the low prevalence schools (New Buipe and Daboya). The use of colour charts for recall of urine colour as opposed to direct questioning, significantly improved the ,c sensitivity, and predictive values in both low and high prevalence schools. Both the school teachers and guineaworm volunteers performed well in respect of questionnaire administration and reagent strip testing. The use of questionnaires cost two times less than reagent strip testing and 25 times less than microscopy in communities with and without schools, whilst the combined use of questionnaires and reagent strips was 12 times and 14 times less in communities with and without schools respectively. About 93% of the children interviewed experienced blackfly bites in the rainy season. The key informant respondents also indicated rainy season as most important for fly nuisance. The 50% or more bites had the highest K for fly nuisance and is thus the best community cut-off for blackfly nuisance monitoring in the study area. There was no significant difference in blackfly nuisance with respect to proximity of communities to potential breeding sites (P>0.05, Mann-Whitney U-test, 95% Cl). The cost of US$ 125 per surveyed community or school under general expenditure represents the logistical expenses for all the diseases and insect vectors included in the questionnaires and this underscores the cost-effectiveness and need to integrate guineaworm surveillance with the monitoring of other health conditions, insect vectors as well as relevant occurrences at the community level.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Doctor of Philosophy, 1998