What this test measures
A stool routine and microscopy combines a macroscopic exam (colour, consistency, mucus, blood, undigested food, worms), a chemical exam (pH, occult blood, reducing substances when needed) and a microscopic exam of a wet-mount slide. Microscopy looks for red blood cells, pus cells (WBCs), parasitic ova (eggs) and cysts, trophozoites (Entamoeba histolytica, Giardia), larvae (Strongyloides), fat globules, muscle fibres, starch granules, and yeast.
This is the most widely ordered stool test in Indian outpatient and paediatric practice — comprehensive, low-cost, and high-yield for the diarrhoea / dysentery / malabsorption questions that come through the clinic daily.
Why it matters
Helminthic infestation, amoebiasis, giardiasis and bacterial dysentery remain very common in India, especially in children and people exposed to unsafe water. A single stool R/M can pick up ascaris and hookworm eggs, amoebic trophozoites with ingested RBCs, giardia cysts, and the classic mucus-with-blood pattern of bacillary dysentery — guiding specific treatment immediately.
It is also a primary tool for evaluating chronic diarrhoea, suspected malabsorption (steatorrhoea — visible fat droplets), GI bleeding, and inflammatory bowel disease. The combination of macroscopic + chemical + microscopic findings often answers the clinical question in a single sample.
How to prepare
Collect a small fresh stool sample in a clean, dry, leak-proof container from the lab. Sample the most abnormal-looking part (with mucus / blood / worms if present). Avoid contamination with urine or toilet water. Send within 1 hour for best parasite detection (trophozoites die quickly outside the gut). For chronic parasitic infections, three samples on alternate days are recommended because egg shedding is intermittent. Avoid antibiotics, antidiarrhoeals, laxatives and barium contrast for 7 days if possible. Avoid testing during menstruation.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| RBCs (microscopy) (/HPF) | Absent | Normal. | RBCs in stool: dysentery (bacterial or amoebic), inflammatory bowel disease, colorectal polyps / cancer, haemorrhoids. Pair with culture and colonoscopy if persistent. |
| WBCs / Pus cells (microscopy) (/HPF)[1] | Absent or rare | Few or absent — argues against invasive bacterial infection (Shigella, Salmonella, invasive E. coli). Consistent with viral or osmotic diarrhoea. | Many pus cells (> 10–20 / HPF) → invasive bacterial colitis, IBD, amoebic colitis. Culture is the next step. |
| Ova / Cysts of parasites (—)[1][2] | Not seen | Not detected (one negative sample does not rule out — shedding is intermittent). | Identifies the organism: Ascaris lumbricoides, hookworm (Ancylostoma / Necator), Trichuris, Hymenolepis, Taenia, Giardia cysts, Entamoeba cysts. Treatment is targeted to the organism. |
| Trophozoites (—) | Not seen | Not detected. | Motile Entamoeba histolytica trophozoites with ingested RBCs → amoebic dysentery (urgent — treat with metronidazole + luminal agent). Giardia trophozoites → giardiasis (treat with tinidazole / nitazoxanide). |
| Fat globules (steatorrhoea) (—) | Absent | Normal. | Fat globules in stool → fat malabsorption: pancreatic insufficiency, coeliac disease, tropical sprue, biliary obstruction, short-bowel syndrome. Pair with quantitative 72h faecal fat, anti-tTG IgA, and pancreatic elastase. |
Common stool microscopy patterns
| Pattern | Likely cause |
|---|---|
| Many WBCs + RBCs + mucus | Bacillary or amoebic dysentery |
| Trophozoites with ingested RBCs | Entamoeba histolytica (amoebic colitis) |
| Giardia cysts / trophozoites | Giardiasis (chronic diarrhoea, malabsorption) |
| Ascaris / hookworm ova | Helminthic infestation (very common in Indian children) |
| Fat globules + muscle fibres | Pancreatic insufficiency or coeliac disease |
| Watery stool, no RBCs / WBCs / parasites | Viral gastroenteritis (rotavirus, norovirus) |
| Reducing substances + low pH | Carbohydrate malabsorption (often lactose) |
Frequently asked questions
How do I collect the stool sample correctly?
Pass stool onto a clean dry surface (cling film over the toilet works) or a clean container. Use the scoop in the lab kit to transfer a thumb-sized portion — include any mucus, blood or worm pieces. Avoid contamination with urine or toilet water.
How fresh does the sample need to be?
Within 1 hour for best parasite detection — trophozoites die quickly outside the body. If you cannot deliver within an hour, refrigerate at 4°C (not frozen) and deliver within 12 hours.
Why do I need three samples on alternate days?
Many parasites shed eggs intermittently, so a single sample can miss the infection. For chronic diarrhoea, suspected amoebiasis or giardiasis, three samples on alternate days improves detection significantly.
What does "ova not seen" mean — am I parasite-free?
Not necessarily. A negative single sample does not rule out parasitic infection. If symptoms persist, repeat the test 2–3 times on alternate days, or do specific antigen / PCR testing for Giardia and amoeba.
My child has worms visible in the stool — what next?
Bring a sample with the worm to the lab — species identification guides treatment. Albendazole or mebendazole covers most common worms; tapeworms need specific treatment. Family members may also need treatment.
Should I take antibiotics before the test?
No — avoid antibiotics for at least 7 days before if possible, as they suppress organism shedding and confound the result.
How long does the report take?
NABL labs typically deliver stool R/M reports within 4–6 hours.
Related Microbiology / Urine / Stool tests
Tests commonly ordered alongside STOOL ROUTINE AND MICROSCOPY, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Stool Tests · accessed 2026-05-30T00:00:00.000Z
- WHO — Basic Laboratory Methods in Medical Parasitology · accessed 2026-05-30T00:00:00.000Z
- CDC DPDx — Laboratory Identification of Parasites · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Stool Analysis · accessed 2026-05-30T00:00:00.000Z
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