[Evaluation of 2 immunologic techniques (ELISA, DIF) for the diagnosis of Giardia lamblia in feces].

BACKGROUND: Two immunology techniques (ELISA and DIF) were evaluated for the detection of Giardia lamblia in faeces, using microscopic examination as reference method. METHODS: Stool specimens from 378 patients were studied, in our laboratory for detection of G. lamblia. All were examined visually by microscope after carrying out the concentration technique with Para-Pak Macro-Con (Meridian Diagnostics, Cincinnati, Ohio). The ELISA technique (Giardia Celisa Test Cellabs Diagnostics PTY LTD, Brookvale, Australia) was used on the 378 faeces specimens and 294 of them were processed also by DIF (Giardia-Cel IF Test, from the same commercial supplier). RESULTS: A total of 16 positive visual detections was obtained. Bot the ELISA and DIF techniques showed an excellent sensitivity (100% for both) and specificity (97.5% and 98.5%) respectively, as well as a negative predictive value of 100% for ELISA and DIF, whilst the positive predictive value is reduced to 79% in DIF and 64% in ELISA. CONCLUSIONS: From our point of view, both tests are of utility for the screening of carriers, for epidemiological analyses, for the study of outbreaks of diarrhoea due to contaminated waters, as well as non-invasive methods for diagnosis in suggestive clinics with negative microscopic examinations.