The Effectiveness of Light Microscopy, Immunofluorescence Assays, ELISA, Culture, and PCR in Detecting Blastocystis sp Infection
[Efektywność mikroskopii świetlnej, testów immunofluorescencji, ELISA, hodowli i PCR w wykrywaniu zakażenia Blastocystis sp.]

Streszczenie
Blastocystis sp. jest pierwotniakiem pasożytującym w jelicie grubym człowieka. Występuje w różnych krajach ze zmienną częstością, od 0,5% w Japonii, do ponad 60% w Indonezji. W piśmiennictwie spotyka się opinie o nieszkodliwości, jak również doniesienia o jego  chorobotwórczości, zwłaszcza u chorych ze znacznym obniżeniem odporności. Istnieje kilka, różnie ocenianych w piśmiennictwie, metod wykrywania Blastocystis sp. w kale, dlatego ważna jest ocena detekcji tego pasożyta, zapewniająca możliwie najwyższą czułość i swoistość diagnostyczną.

ABSTRACT
Introduction: Blastocystis is probably the most common enteric parasite in humans globally. Although the role of Blastocystis in human disease is still controversial, the evidence suggests that pathogenicity may be associated with certain subtypes of the protist. Immunocompromised patients seem to be prone to Blastocystis infection. It is not always known if Blastocystis is the real reason of infection or standby passenger. Detection of Blastocystis in faeces can be performed by means of different techniques: light microscopy, direct immunofluorescence and ELISA as well as culture or detection of parasite DNA. The first three methods are the most common used, whereas culture and PCR are considered as definitive methods. Any unequivocal protocol of testing for Blastocystis infection has not been proposed and use of different techniques can leads to discrepant results and misdiagnosis.
The objective of this study was to perform the assessment of: light microscopy, direct immunofluorescence and ELISA in comparison to definitive methods: culture and PCR in order to develop sensitive and specific laboratory diagnostic protocol.
Materials and methods: Total number of 43 fecal samples were included to the experiment. 36 samples were collected from 33 patients with hematologic malignancies with abdominal pain or diarrhea, next 7 samples from otherwise healthy individuals form the National Institute of Public Health in Warsaw as positive control samples.
Results: Diagnostic specificity values calculated for light microscopy and immunofluorescence were high: 93% and 97% respectively, whereas for diagnostic sensitivity was only 50% and 38% respectively. For ELISA both values: sensitivity 64% and specificity 76% were unsatisfactory.
Conclusions: The positive result in light microscopy or direct immunofluorescence confirms Blastocystis infection, whereas negative result should be confirmed by culture and/or PCR. The relatively low diagnostic sensitivity and specificity of ELISA indicate that any ELISA result should be confirmed via one or two definitive methods.