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Intensity of responses to Cryptosporidium antigen: per cent of sera samples (95% CI) with a response ⩾20% of the positive control
Positivity ⩾20% of positive control; χ2=37·2 (P<0·0001, 3 d.f.).
Positivity ⩾20% of positive control; χ2=13·0 (P<0·01, 3 d.f.).
For example, 80% of persons had sera with a high response defined as ⩾20% of positive control.
