Enhanced detection rate of typhoid fever in children in a periurban slum in Karachi, Pakistan using polymerase chain reaction technology

Objective. Yield of blood culture in clinically suspected cases of typhoid fever is low, whereas indirect serological diagnostic tests are unreliable. Hence, polymerase chain reaction (PCR)-based detection of Salmonella enterica Serovar typhi was used as an aid for diagnosis of typhoid fever in addition to other diagnostic tests. Two periurban communities in Karachi were selected for an epidemiological study of typhoid fever. The aim of the study was to assess whether PCR increased the detection rate of typhoid fever in children in the community. Material and methods. Children aged 2 to 14 years presenting with fever lasting for three or more days were selected. PCR using Hashimoto's protocol based on ViaB gene sequence was used in addition to blood culture and other serological tests. Results. Of the 214 children included in the study, blood culture was found positive for S. enterica S. typhi in 26 (12.4%) cases, whereas 24 children (11.7%) were diagnosed as suffering from typhoid fever when the PCR-based method was used. Both tests were positive in only 10 (4.9%) children. The number of children found positive for either test was 40. PCR increased the rate of detection of typhoid fever by 51%. Conclusion. The sensitivity, specificity, +ve and -ve predictive values of PCR in this study were 40%, 93%, 45% and 92%, respectively.