The Mantoux test, also known as the tuberculin skin test (TST), remains a primary diagnostic screening tool for detecting infection with *Mycobacterium tuberculosis*. Tuberculosis (TB) is a chronic, airborne bacterial infection that predominantly affects the pulmonary system, though it can spread to extrapulmonary sites. When an individual inhales droplet nuclei containing the bacterium, macrophages phagocytize the bacilli in the alveoli, initiating a cell-mediated immune response. The Mantoux test is designed to measure this delayed-type hypersensitivity reaction rather than active disease presence alone. It cannot distinguish between latent tuberculosis infection (LTBI) and active TB disease. Therefore, positive skin test results require further clinical evaluations, including chest radiography and sputum microscopy, to confirm active infection before initiating treatment protocols in Nigerian healthcare facilities.
Performing a valid Mantoux test requires specific, standardized equipment to ensure accurate antigen delivery. Nurses must assemble the following items before procedure initiation:
PPD vials must be stored continuously between 2°C and 8°C in a refrigerator and protected from direct light. Freezing destroys the potency of the tuberculin proteins, rendering the test invalid. Always check the expiration date and inspect the vial for particulate matter or discoloration prior to drawing the dose.
Administering the Mantoux test demands precise intradermal technique to deposit the antigen correctly into the dermal layer of the skin.
Reading a Mantoux test requires precise timing and specialized physical assessment skills. The immune reaction peaks between 48 and 72 hours post-injection, meaning the patient must return within this specific window. If a patient fails to return by 72 hours, the test is generally considered invalid, and a repeat test must be scheduled.
To read the result, the nurse uses palpation rather than visual inspection alone to trace the borders of the induration. Induration is the hard, dense, raised area resulting from cellular infiltration, which differs from soft, red erythema. Using a specialized flexible ruler, the nurse measures the transverse diameter of the induration perpendicular to the long axis of the forearm. Erythema should be ignored during measurement, as only the palpable induration dictates the clinical interpretation.
Interpreting the induration size depends heavily on the patient's individual risk profile and medical history rather than a single universal threshold. Nigerian clinical guidelines categorize induration findings into three distinct cut-off tiers:
| Induration Threshold | Patient Risk Category | Examples |
|---|---|---|
| ≥ 5 mm | High risk | HIV-positive individuals, recent close contacts of active TB cases, immunosuppressed patients |
| ≥ 10 mm | Moderate risk | Healthcare workers, residents of high-risk congregate settings, recent immigrants from high-burden countries |
| ≥ 15 mm | Low risk | Individuals with no known risk factors for tuberculosis infection |
A reading that falls below the designated threshold for a specific risk group is interpreted as negative for tuberculosis infection.
The Mantoux test is a screening tool, not a diagnostic absolute, meaning both false-positive and false-negative outcomes occur frequently in clinical practice.
Nurses play a vital role across every phase of the tuberculin screening process. Before administration, the nurse must assess for contraindications, such as a documented previous severe reaction or extensive skin burns at the injection site. During the procedure, clear instruction prevents patient anxiety and ensures adherence to follow-up visits.
Patients must be instructed not to scratch, bandage, or apply topical creams to the injection site. They need to understand the critical importance of returning to the clinic between 48 and 72 hours for reading. Post-reading, the nurse documents the injection site, date, time, type of tuberculin used, manufacturer, lot number, and the exact millimeters of measured induration in the patient record.