Apropos “Evaluation of Serological Diagnostic Tests for Typhoid Fever in Papua New Guinea Using a Composite Reference Standard”

LETTER

We compliment the investigators at the Institute of Medical Research and the Central Hospital at Goroka, Papua New Guinea, for their meticulous blood culture- and molecular investigation-based valuation of serological tests for typhoid diagnosis (1). As with other resource-poor counties, there is a paucity of sophisticated laboratory infrastructure and trained staff for carrying out either blood culture or any molecular investigation. Obviously, the local standardization of the individual laboratory's output would have to take place through a cheaper and simpler but reliable line of attack.

A beginning could be made with the slide Widal test itself. Diagnostic laboratories, including those in remote locations, even if lacking trained personnel or sophisticated instrumentation, could be encouraged to pick up blood samples from patients with high or low titers of Salmonella enterica serovar Typhi antibodies. By testing such aliquots repeatedly, it would be possible to work out the local mean antibody titer and standard deviation (SD) (2). If the results of this basic investigation to diagnose typhoid fever in remote laboratories are consistently satisfactory, it can be presumed that the results of other investigations would also be valid.

We feel that such activity for basic local quality control, with minimal financial or manpower input, would be very valuable for clinical diagnostic laboratories attached to the Institute of Medical Research, the Goroka Central Hospital, or elsewhere in Papua New Guinea for standardization of diagnostic kits procured from different suppliers. The quality of kits for laboratory diagnosis of typhoid fever (conventional Widal test or the dot immunoassay- or immunochromatography-based IgM and/or IgG formats) would not be consistent with different manufacturers (3).

In conclusion, such basic internal quality control for serological tests to diagnose typhoid fever would assist in standardization of any multicentric studies to determine the background titers in an asymptomatic population (3).