Decision analysis: an aid to the diagnosis of Whipple's disease.

BACKGROUND: Diagnosis of Whipple's disease, a rare systemic infection affecting predominantly the small bowel, is based on the identification of the bacterium Tropheryma whipplei.

AIMS: To make explicit diagnostic uncertainties in Whipple's disease through a decision analysis, considering two different clinical scenarios at presentation.

METHODS: Using appropriate software, a decision tree estimated the consequences after testing different strategies for diagnosis of Whipple's disease. Probabilities and outcomes to determine the optimum expected value were based on MEDLINE search.

RESULTS: In patients with clinically-predominant intestinal involvement, diagnostic strategies considering intestinal biopsy for histology (including appropriate staining) and the polymerase chain reaction testing for bacterial DNA were similarly effective. In case of failure of one procedure, the best sequential choice was a polymerase chain reaction analysis after a negative histology. Of the five strategies tested for cases with predominant focal neurological involvement, the stereotaxis cerebral biopsy evidenced the highest expected value. However, using quality-adjusted life-years considering the morbidity of methods, intestinal biopsy for PCR determination was the best choice.

CONCLUSIONS: In patients with Whipple's disease having predominant digestive involvement, intestinal biopsies for histology should be indicated first and, if negative, a bacterial polymerase chain reaction determination should be the next option. Although the molecular polymerase chain reaction assessment of cerebral biopsies has the highest diagnostic yield in neurological Whipple's disease, its associated morbidity means that analyses of intestinal samples are more appropriate.