Counts and cards – a novel way to detect typhoid infections in the ED

Objective

The diagnosis of typhoid fever is made by growth of the causative microorganism from culture of bone marrow aspirate or blood which is time dependent. In a busy ED like ours, typhoid fever is a frequent presentation. There is need for a rapid and reliable test made available at the bed side, to detect typhoid infections. The sensitivity and specificity of Enterocheck WB, a card test that detects IgM antibodies to salmonella typhi and low eosinophil counts were compared individually and together, with the gold standard of blood culture using BacT/Alert.

Methods

Setting - Multi specialty community based teaching hospital in Chennai with about 1500 ED visits per month

Number of subjects – 95.

Study design - Retrospective study done from January 2012 for a period of 1 year.

Results

For 4 or lesser days of fever, typhoid IgM had sensitivity of 66.67%, specificity of 40%. For 5 or greater days of fever, sensitivity was 75.61%, specificity 50%.

Eosinophil count was persistently low (0.09%) in all typhoid cases irrespective of day of presentation of fever.

Sensitivity of a low eosinophil count was 100%, specificity being 14.8%.

In all culture positive cases, sensitivity of IgM and low eosinophil counts together was 100%. For all culture negative cases, specificity was 92.3%. So both IgM and eosinophil count together have a high specificity as well as sensitivity.

Limitations

This was a retrospective study. Prospective study is awaited to reconfirm the results.

Conclusion

The typhoid IgM test can be performed at the bedside in the ED. Eosinophil count can be easily obtained from a CBC. In conjunction, they can accurately detect salmonella infections for early initiation of appropriate treatment in the ED itself, thereby saving time, money and precious hospital beds.