Independent evaluation of onchocerciasis rapid assessment methods in Benue State, Nigeria.
OBJECTIVE
To evaluate the prevalence of palpable nodules or skin depigmentation as rapid indicators of onchocerciasis epidemicity in at-risk communities.


METHODS
We examined data collected in Benue State on 11035 individuals in 32 villages to evaluate these rapid assessment methods.


RESULTS
The prevalence of palpable nodules correlates more closely with microfilarial prevalence (r=0.68, P<0.001) and community microfilarial load (r=0.64, P<0.001) than the prevalences of skin depigmentation or other potential rapid indicators. The recommended cut-off value for palpable nodules of 20% or more in males aged >20 years had a sensitivity of 94% and specificity of 50% compared to a cut-off of 40% or more for microfilarial prevalence in all ages. This would mean that in these 32 villages 17 of 18 would have been correctly identified for treatment, and a further 7 at lesser risk would have been targeted for treatment.


CONCLUSIONS
Skin snipping and parasitological examination can be replaced by the simpler method of palpating onchocercal nodules to identify communities at serious risk of onchocerciasis. This has important operational benefits for onchocerciasis control programmes.
Whitworth
J A
JA
Tropical Health Epidemiology Unit, London School of Hygiene and Tropical Medicine, UK. mrc@starcom.co.ug
Gemade
E
E
D000293:Adolescent; D000328:Adult; D001706:Biopsy / Q000379:methods; D002648:Child; D002675:Child, Preschool; D019353:Endemic Diseases / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D017496:Hypopigmentation / Q000469:parasitology* / Q000473:pathology*; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D009549:Nigeria / Q000453:epidemiology; D009748:Nutrition Disorders / Q000150:complications / Q000453:epidemiology; D009855:Onchocerciasis / Q000150:complications* / Q000453:epidemiology / Q000473:pathology*; D010173:Palpation / Q000379:methods*; D010808:Physical Examination / Q000379:methods*; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity