ABSTRACT
A study from Malawi attempted to assess the sensitivity and specificity of directly observable clinical signs for the diagnosis of malaria and pneumonia in children. In the absence of microbiological results, the diagnosis of streptococcal infection in patients who are present with a sore throat is often difficult. The two main terms used to describe how well a test performs are sensitivity and specificity. These two terms are not very fortunate, partly because they are too similar and partly because they do not give any intuitive feeling for what they mean. In asymptomatic carriers, the sensitivity of one faecal culture is only around 70%. The association between length of relationship and chlamydia infection actually becomes somewhat stronger when misclassification is accounted for. The Random misclassification was about disease versus no disease, but the same reasoning applies if exposure had been randomly misclassified.
