What this test measures
A sputum sample (deep cough from the lungs, not saliva) is tested in one of several ways: (1) Ziehl-Neelsen / fluorescent smear microscopy to look for acid-fast bacilli (AFB) — a quick, cheap test that is positive when bacterial load is high; (2) Xpert MTB/RIF (CB-NAAT) — a molecular test that detects Mycobacterium tuberculosis DNA and rifampicin resistance in 2 hours, now the recommended first-line test in India's National TB Elimination Programme (NTEP); (3) sputum culture — the gold standard but takes 2–8 weeks.
"1 day" sputum usually refers to a single morning sample (spot or early morning) — useful for spot diagnosis. Current NTEP guidance recommends two samples (spot + early morning) for smear microscopy or a single sample for Xpert MTB/RIF, which is more sensitive.
Why it matters
India has the world's highest burden of tuberculosis — accounting for roughly a quarter of global TB cases. Sputum microscopy / Xpert is the entry point to the National TB Elimination Programme (NTEP), which provides free testing and treatment. Anyone with a cough lasting more than 2 weeks, fever, night sweats, weight loss or haemoptysis should be tested.
WHO and NTEP now recommend Xpert MTB/RIF as the initial test wherever available — it detects 90% of smear-positive and roughly 70% of smear-negative culture-positive TB, plus rifampicin resistance — a marker of MDR-TB. Free testing is available at all Designated Microscopy Centres (DMCs) under NTEP.
How to prepare
Sample should be a deep cough from the chest (not saliva or nasal secretions). Rinse mouth with water before collection (no toothpaste). The first morning sample (after waking, before food) is the best — secretions pool overnight. Collect into a sterile wide-mouth container; submit within 1–2 hours or refrigerate. Trained staff at NTEP centres can guide collection.
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 |
|---|---|---|---|
| Sputum AFB Smear (Result)[1][2] | Negative (no AFB seen) | Negative smear does not rule out TB — sensitivity is only 50–60%. If suspicion is high, repeat / send for Xpert MTB/RIF or culture. | Positive smear — confirms pulmonary TB and infectiousness. Reported as 1+, 2+, 3+, or scanty (number of AFB per field). Higher grades = more infectious. Treatment is started immediately under NTEP, and household contacts are screened. |
| Xpert MTB/RIF (CB-NAAT) (Result)[1] | MTB Not Detected | MTB Not Detected — strongly suggests no active TB, but a small fraction of culture-positive paucibacillary cases can be missed. Clinically suspicious cases need culture / additional testing. | MTB Detected (Low / Medium / High / Very Low) — confirms TB; reports rifampicin resistance status. Rifampicin Resistance Detected — likely MDR-TB; refer to NTEP DR-TB centre for line probe assay and full drug-susceptibility testing. |
Sputum tests for TB diagnosis
| Test | Time to result | Sensitivity | Detects resistance | NTEP availability |
|---|---|---|---|---|
| Ziehl-Neelsen smear | Same day | 50 – 60% | No | Universal (DMCs) |
| Fluorescent (LED) microscopy | Same day | 60 – 70% | No | Widespread |
| Xpert MTB/RIF (CB-NAAT) | 2 hours | ~ 90% | Yes (rifampicin) | Increasing, NTEP recommended first-line |
| Xpert MTB/RIF Ultra | 2 hours | > 90% (better in HIV / smear-neg) | Yes (rifampicin) | Selected centres |
| Sputum culture (solid / liquid) | 2 – 8 weeks | Gold standard | Yes (full DST) | Selected referral labs |
Frequently asked questions
When should I get a sputum test?
NTEP recommends sputum testing for anyone with cough lasting more than 2 weeks, fever / night sweats, unexplained weight loss, or haemoptysis (coughing blood). Earlier evaluation is appropriate in people with HIV, diabetes, or contact with TB.
Do I need to fast?
No fasting, but rinse mouth with water before collection (no toothpaste, no food residue). The first morning sample is best.
What is the difference between smear and Xpert?
Smear microscopy looks for the bacteria directly under a microscope — cheap, quick but less sensitive. Xpert MTB/RIF (also called CB-NAAT) is a molecular test that detects TB DNA and rifampicin resistance — more sensitive, faster, but more expensive. NTEP now recommends Xpert as the initial test wherever available.
Is sputum testing free in India?
Yes — under the National TB Elimination Programme (NTEP), sputum smear microscopy, Xpert MTB/RIF and TB treatment are all free at government Designated Microscopy Centres and TB Units. Private labs charge a fee.
My smear is negative but I have symptoms. Could I still have TB?
Yes — smear microscopy misses about 40% of culture-positive TB cases. If clinical suspicion is high, your doctor should request Xpert MTB/RIF and / or chest X-ray and sputum culture. HIV-positive patients are more likely to have smear-negative TB.
What does "rifampicin resistance detected" mean?
It strongly suggests multi-drug resistant TB (MDR-TB). You will be referred to an NTEP DR-TB centre for line probe assay and full drug-susceptibility testing, and started on the appropriate second-line regimen. Free, supervised treatment is available.
How many sputum samples should I give?
For smear microscopy, NTEP recommends two samples — a spot sample and an early-morning sample. For Xpert, a single good-quality sample is enough. Follow the guidance at your DMC.
Is sputum the only test for TB?
No — chest X-ray, IGRA / Mantoux (for latent TB), CT chest, urine LAM (for advanced HIV), and tissue biopsy / culture for extra-pulmonary TB are also used. Sputum is the entry point for pulmonary TB.
Related Other / Biochemistry tests
Tests commonly ordered alongside SPUTUM 1 DAY, or that help interpret an unexpected result.
Sources & references
- Central TB Division — NTEP Technical and Operational Guidelines · accessed 2026-05-30T00:00:00.000Z
- WHO — Sputum Smear Microscopy and Xpert MTB/RIF · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Tuberculosis Diagnosis · accessed 2026-05-30T00:00:00.000Z
- ICMR — TB Diagnostic Algorithms · accessed 2026-05-30T00:00:00.000Z
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