[Criterion on the screening for acute flaccid paralysis (AFP) surveillance]

Using AFP as the criterion for surveillance of children aged < 15 years on polio eradication programme, the sensitivity is 100%. But specificity is low, with high false positivity. Through analysing all 818 cases of AFP occurred in 1991 in Anhui province, we were trying to find out a more specific criterion for the purpose of screening polio cases from AFP. Among 818 cases of AFP aged < 15 years, most polio and non-polio AFP cases occurred under 5 years. At the onset of paralysis, 87.63% of the polio cases presented with fever, compared with 45.99% of non-polio AFP cases did. There fore we chose age and fever at the onset of paralysis as the criterion for screening tests. In parallel tests, the sensitivity was very high, but the specificity was still low. In serial tests, the combination of age under < 6 and fever at onset of paralysis resulted in a sensitivity of 81.44% and specificity of 65.54%. This results suggested that by screening the cases of AFP aged < 6 years who had fever at the onset of paralysis, the number of sample size under testing can be largely reduced, with a minimal compromise in the sensitivity. As for surveillance purpose, the criterion can be used to identify more critical cases followed by urgent attention.