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The latex agglutination immunoassay is a diagnostic technique for the determination of gastrointestinal bleeding disorder through the investigation of hemoglobin (Hb) concentration (conc.). This differs from the immunochromatography (IC) method which requires the observation of band patterns on a test pad to determine negative or positive results. The research objective is to investigate suitable Hb conc. in fecal samples to indicate positive and negative results in latex agglutination immunoassay through the comparison of results with the IC method. The study was conducted using 116 fecal specimens from patients who attended Thammasat University Hospital, Pathum Thani province. ROC curve and Chi-square test were used to explore the appropriate Hb conc. and association analysis with IC method. The result illustrated the most appropriate cut-off of Hb conc. at 41 nanogram per milliliter (ng/ml) which provided percent of sensitivity, specificity and correctly classified are 95.45, 72.00 and 85.34 % respectively. Moreover, this Hb conc. provides power of discrimination of 91.91, within confidence interval of 87.00 to 97.00 %. These results can be considered as outstanding. In conclusion, the study revealed that the cut-off Hb. conc. at 41 ng/mL in latex agglutination immunoassay provides the best percentage of sensitivity and good specificity when compared with IC method. Although, erythrocyte count by light microscope is not related to IC method, average count is significantly different between positive and negative results in IC method. The aim of future research should be to evaluate latex agglutination immunoassay combined with other factors in order to improve efficiency of screening diseases.
Keywords: agglutination; immunoassay; immunchromatography; bleeding; gastrointestinal tract
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