Laboratory testing for Entamoeba histolytica
| Specimen | Details | Sensitivity | Specificity | Pros | Cons | |
| Light microscopy | Stool | Can visualise cysts but cannot differentiate E. histolytica from non-pathogenic cysts. May visualise trophozoites in ‘hot stool’ (stool examined as soon as it is produced) | <60%6 | 95%144 | Cheap Widely available Can screen for other parasites | Low sensitivity and specificity Stool tests cannot diagnose extraintestinal infection |
| Antigen testing ELISA | Stool or liver abscess aspirate | Test for E. histolytica-specific antigens | Up to 88%6 | >80%6 | Can differentiate Entamoeba species Widely available | Need fresh (not preserved) stool Reduced sensitivity and specificity once therapy started and for carriers |
| PCR* | Stool and liver abscess aspirate | Test for E. histolytica-specific genes Gold standard for intestinal amoebiasis | 92%–100%6 | 89%–100%6 | Can differentiate Entamoeba species | Expensive Requires laboratory skill E. histolytica may not feature in routinely tested pathogen panels |
| Serology/antibody testing | Serum | Detects IgG to E. histolytica-specific antigen | 65%–92%6 | >90%6 | Useful for both intestinal and extraintestinal infection | Lower sensitivity for intestinal amoebiasis (~ 60%) than ALA (~95%). Suitable for use in non-endemic regions False positives in endemic countries Positive within 7–14 days of symptoms Can remain positive for years after resolution of infection |
| Point-of-care antigen detection | Stool | Monoclonal antibody based | 28%–100%101 | 80%–100%101 | Cheap Quick | Cannot differentiate Entamoeba species Low sensitivity |
| Histopathology | Tissue | Light microscopy of formalin-fixed paraffin wax embedded histology specimens, such as colonic biopsies. Trophozoites visible on H&E staining, highlighted by staining with Periodic Acid Schiff | Insufficient data | Operator-dependent | Cheap Routine practice—no requirement for pretest suspicion Can be used on tissue from any site, both biopsies and surgical resections can be reported urgently within 24 hours | Tissue reaction pattern is not specific and can mimic Crohn’s disease. Trophozoites may be missed or misdiagnosed and identification is operator-dependent |
*UK Health Security Agency recommend PCR as the method of choice for diagnosis of E. histolytica in symptomatic and asymptomatic patients.26
ALA, amoebic liver abscess.