Dientamoebiasis - Diagnosis

Diagnosis

Diagnosis is usually performed by submitting a stool sample for examination by a parasitologist in a procedure known as an Ova and Parasite (O&P) Examination. Approximately 30% of children with D. fragilis infection exhibit peripheral blood eosinophilia.

A minimum of three specimens (stool) should be submitted having been immediately fixed in polyvinyl alcohol fixative, sodium acetate-acetic acid-formalin fixative, or Schaudinn's fixative as the protozoan does not remain morphologically identifiable for long. Further, all specimens, regardless of consistency, should be permanently stained prior to microscopic examination with an oil immersion lens. The disease may remain cryptic due to the lack of a cyst stage if these recommendations are not followed. Dientamoeba fragilis detection methods and prevalence: a survey of state public health laboratories. J H Grendon, R F Digiacomo, and F J Frost Office of Toxic Substances, Washington State Department of Health, Olympia 98504.

The trophozoite forms have been recovered from formed stool, thus the need to perform the ova and parasite examination on specimens other than liquid or soft stools.

DNA Fragment Analysis provides excellent sensitivity and specificity when compared to microscopy for the detection of D. fragilis and both methods should be employed in laboratories with PCR capability.

The most sensitive detection method is parasite culture, and the culture media require the addition of rice starch.

An indirect fluorescent- antibody (IFA) for fixed stool specimens has been developed.

1. One researcher investigated the phenomenon of symptomatic relapse following treatment of infection with Dientamoeba fragilis in association with its apparent disappearance from stool samples. The study found that the organism could still be detected in patients through colonoscopy or by examining stool samples taken in conjunction with a saline laxative.
2. A study found that trichrome staining, a traditional method for identification, had a sensitivity of 36% (9/25) when compared to stool culture.
3. An additional study found that the sensitivity of staining was 50% (2/4), and that the organism could be successfully cultured in stool specimens up to 12-hours old that were kept at room temperature.