Human African trypanosomiasis (HAT) is characterized by a non-specific clinical presentation with no consistent, pathognomonic manifestations. However definite diagnosis is necessary to avoid unnecessary therapeutic risks with toxic drugs. Further complicating this situation is the frequent need to achieve field diagnosis in remote locations with limited facilities.

Serological tests such as CATT (card agglutination trypanosomiasis test) are useful for initial population screening to identify suspects but are not sufficiently reliable for definitive diagnosis since the variations in sensitivity and specificity have been observed between countries and disease pockets. Parasitological examination is still the only method of definitive diagnosis. Thresholds of trypanosome detection differ from one technique to another, i.e., 10,000 trypanosomes per millilitre  for fresh blood smears, 5,000 ml for thick drop specimens stained with Giemsa, 500 ml for centrifugation in capillary tubes, less than 500 ml for the QBC test, and 100 ml for the ion exchange minicolumn system. The possibility that the QBC test and minicolumn anion exchange system may go out of production could pose a serious problem for field diagnosis. Decisional algorithms are being developed to optimize use of remaining techniques.

Because HAT has limited geographic distribution, an appropriate history of exposure should be identifiable. Diagnosis of the disease requires significant human and material resources, such as well-equipped health centers and qualified staff. Because such resources are lacking in most endemic areas, the majority of people with HAT die before they are diagnosed.