Introduction Entamoeba (E.) histolytica is one of the intestinal protozoan that causes a disease known as "amoebiasis", which is the third leading parasitic disease, after malaria and schistosomiasis, causing death in humans. According to World Health Organisation (WHO) estimates, E. histolyticamay may infect half-a-billion people annually and is responsible for 40,000 to 100,000 deaths a year. 1 In tropical regions, amoebiasis is more common among the general population and particularly among patients attending hospitals and healthcare centres with diarrhoea, abdominal pain, and fever. 2 E. histolyticais pathogenic amoeba causing damage to intestinal mucosa, amoebic colitis, haematogenous spread, producing fatal abscesses and extra-intestinal amoebiasis. 3 The inflammatory and necrotic activities of this parasite alter blood parameters, cause anaemia, cholestasis and inflammation, and are marked by appearance of natural anti-parasitary indicators, increase of antibodies, and liver inadequacy. 4 Amoebiasis is transmitted through the ingestion of mature cysts and is usually acquired from food or water sources contaminated with faeces. 5 Demographic, behavioural, environmental and clinical characteristics that linked with disease are counted among the risk factors. Microscopy, culture analysis and molecular techniques are applied for E. Histolytica detection. All these diagnostic techniques have some limitation. Studies on amoebiasis in Pakistan are based on microscopic examination of faeces, which leads to poor sensitivity and confounded with false-positive (FP) results due to misidentification of macrophages as trophozoites, polymorphonuclear leukocytes as cysts and other entamoeba species. 6 Polymerase chain reaction (PCR) is a powerful tool, but is technically complex, costly, J Pak Med Assoc 1777 ORIGINAL ARTICLE Seroprevalence and associated risk factors of Entamoeba histolytica infection among gastroenteritis patients visiting the public healthcare system, Pakistan Bisma Khan, 1 Kiran Afshan, 2 Sabika Firasat, 3 Mazhar Qayyum 4 Abstract Objectives: To investigate the seroprevalence and associated risk factors of entamoeba histolytica among patients with gastrointestinal complaints, and to measure the eventual changes in serum biochemical parameters to reflect its pathogenicity. Methods: The cross-sectional study was conducted in different hospitals of Potohar region in Punjab province and in the Khyber Pakhtunkhwa province of Pakistan from September2015 to February 2017, and comprised individuals of either gender belonging to diverse backgrounds, inhabiting different areas of the country. The patients were enrolled from among those who visited outpatient departments with complaints of vague abdominal pain, nausea, vomiting, indigestion and diarrhoea. Blood samples were screened by using enzyme-linked immunosorbent assay and serum biochemical tests. Data was analysed using SPSS 20. Results: Of the 356 subjects, 238(66.9%) were females and 118 (33.1%) were males. The overall mean age was 33.4±11.05 years. Seroprevalence of entamoeba histolytica was 356(73%). The infection rate did not differ significantly (p>0.05) among cities, while the highest infection was recorded in Islamabad 91(25.5%). The participants in rural areas had 2.16-fold higher risk of infection compared to urban areas, while the lowest risk of infection among people aged 50years compared to those aged 40-49 years (p=0.04). The amoebiasis was significantly associated with eating unwashed raw vegetables and average toilet facilities. Among clinical complications, haemodynamic changes, jaundice, vomiting, haemoglobin level, loose motion, intolerance to oral feeding, and history of antibiotics were significant associated variables (p<0.05 each). Significant elevation in alkaline phosphatase, aspartate aminotransferase, total protein and globulin levels were positively associated with amoebiasis (p<0.01 each). Conclusion: In entamoeba histolytica -positive patients ,serum biochemical level was found elevated and the risk factors determined were eating unwashed vegetables, toilet facilities, age, locality, jaundice, vomiting, haemoglobin level, loose motion, intolerance to oral feeding, and history of antibiotics. Keywords: Amoebiasis, Biochemical parameters, Risk factors, Serology, Pakistan. (JPMA 69: 1777; 2019) DOI:10.5455/JPMA.300501 1-3 Department of Animal Sciences, Quaid-i-Azam University Islamabad, 4 Department of Zoology and Biology, PMAS-Arid Agriculture University, Rawalpindi, Pakistan. Correspondence: Kiran Afshan. Email: kafshan@qau.edu.pk