Performance of one-step spanbio™ rapid test in detection of giardia lamblia in Busia county referral hospital, western Kenya

Abstract

The protozoan flagellate parasite Giardia lamblia is the aetiologic agent for giardiasis, an infectious disease with significant burden in developing countries. Currently, clinical signs and symptoms accompanied by microscopy are used to diagnose giardiasis. However, microscopic stool analysis is limited by low sensitivity, labor intensive and high turn-around time. Moreover, polymerase chain reaction (PCR) has been applied in the detection of G.lamblia, but its cost and technical skills have compromised its clinical utilization. One-step rapid diagnostic tests (RDT) such as the SPANBIO™ have been developed for infection screening purposes due to high turn-around time and use in point-of-care testing. SPANBIO™ RDT is based on the principle of immuno-chromography. However, its utility in detection of giardiasis in Kenya has not been evaluated. This was cross-sectional health facility-based study that sought to evaluate the diagnostic performance of SPANBIOTM RDT in detection of Giardia lamblia with microscopy as the gold standard and PCR as a reference standard in a clinical setting. The specific objective were; To determine the specificity of SPANBIOTM RDT against microscopy and PCR in detecting G. lamblia in diarrheal patients, to determine the sensitivity of SPANBIOTM RDT against microscopy and PCR in detecting G. lamblia in diarrheal patients, to identify factors influencing SPANBIOTM RDT test performance in diarrheal patients. Data collection of one hundred and forty-seven stool specimens from microscopy confirmed G. lamblia infected =78 and uninfected =69 individuals, were documented including demographic and clinical information. The patients collected about 10gms of sample (after instructions) from which only 2gms (peas size) were processed and examined macroscopically and microscopically by the direct stool analysis procedure. Subsequently, the stools specimens were analyzed using the SPANBIO™ one-step RDT according to the manufacturer’s protocols. Total genomic DNA extraction was done on 2 gms of stool and PCR was performed by amplification of GDH (5′-TCAACGTCAACCGCTTCCT-3′) gene. Relative to the gold standard SPANBIOTM RDT illustrated a sensitivity of 66.7% (95% CI; 55.1-76.9%) and specificity of 98.6% (95% CI; 92.3-100%) with positive predictive value and negative predictive value of 98.1% (95% CI; 88.1%-99.7%) and 72.3% (95% CI; 65.6-78.1%) respectively; The test agreement between the SPANBIOTM and microscopy was high, and is indicated by Cohenʹs kappa coefficient = 0.6388; P<0.0001). When compared to PCR, RDT had sensitivity and specificity of 78.2 %, (95% CI; 67.4-86.8%) and 89.7% (95% CI; 80.2-95.8%) respectively and a positive predictive value and negative predictive value of 89.7 % (95% CI; 81.0-94.7%) and 78.5% (95% CI; 70.4-84.8%), respectively. The test agreement between the SPANBIOTM and PCR was high, and is indicated by Cohenʹs kappa coefficient = 0.6750; P<0.0001). Analyses to determine factors influencing SPANBIOTM RDT performance indicated that mucus, 2.982(95% CI; 0.089-0.440) and fecal pus 2.318(95% CI; 0.035-0.439) in stool affected its performance, G. lamblia was commonly found in semi-formed and loose stool. Therefore, there should also be a way of improving sample quality for giardiasis diagnosis. In conclusion the results obtained have shown that although mucus and fecal pus influence test performance, SPANBIOTM RDT is equally can be used in the diagnosis of G. lamblia. This study has significance as it has shown that there is an alternative technique that can produce timely, reliable and non-laborious results in the diagnosis of G. lamblia, which can be used in areas without microscopic capabilities.