Table 2. Laboratory diagnostic techniques used and internally compared in the NIDIAG study on persistent digestive disorders.
| Diagnostic technique | Target pathogen(s) | |||
|---|---|---|---|---|
| Soil-transmitted helminths | Schistosoma mansoni | Strongyloides stercoralis | Intestinal protozoa | |
| Direct fecal smear | (✓) | (✓) | (✓) | (✓) |
| Kato-Katz thick smear | ✓ | ✓ | – | – |
| Formalin-ether concentration | ✓ | ✓ | (✓) | ✓ |
| Mini-FLOTAC | ✓ | ✓ | – | (✓)a |
| Baermann funnel concentration | (✓)b | – | ✓ | – |
| Koga agar plate culture | (✓)b | – | ✓ | – |
| RDT for Cryptosporidium and Giardia intestinalis | – | – | – | ✓c |
| POC-CCA urine cassette test | – | ✓ | – | – |
| Acid-fast staining procedure | – | – | – | ✓d |
The laboratory diagnostic techniques consisted of microscopic methods and rapid diagnostic tests (RDTs). They were used and compared within the NIDIAG study on persistent digestive disorders, placing particular emphasis on the suitability for the detection of helminths and intestinal protozoa that may give rise to persistent digestive disorders (≥2 weeks). The following grading system was employed to characterize the suitability of a certain laboratory technique for the detection of specific pathogens: ✓ suitable; (✓) partially suitable; –not suitable.
Of note, additional bacteriologic stool cultures were performed in all countries except Indonesia in case of diarrheic stool samples.
aVery limited published data, according to which FLOTAC techniques may detect some intestinal protozoa species (e.g., G. intestinalis), but further validation of the technique for this use is required.
bHookworm larvae can be detected, in particular by culture. Additionally, hookworm larvae can be found using the Baermann technique, if the stool sample has been kept long enough for the eggs to hatch.
cThis RDT detects only Cryptosporidium spp. and G. intestinalis.
dAcid-fast staining methods (e.g., Kinyoun stain) are particularly suitable for the detection of Cryptosporidium spp., Cyclospora cayetanensis, and Cystoisospora belli that are easily missed by most other microscopic diagnostic techniques.