TB Induration Meter — 3D Printable TST/PPD Reading Tool

A handy, pocket-sized gauge card for measuring tuberculin skin test (TST/Mantoux/PPD) induration. Place the card over the injection site and find the smallest hole that fits over the wheal to quickly read the transverse induration diameter in millimeters.

Hole sizes included: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 20, 25, and 30 mm — covering the full clinical range with 1 mm resolution across the critical 5–15 mm decision zone.

Clinical cutoff values (highlighted in red):

• ≥5 mm — Positive for high-risk individuals (HIV+, immunosuppressed, close TB contacts, abnormal chest X-ray)

• ≥10 mm — Positive for moderate-risk groups (healthcare workers, recent immigrants from high-prevalence countries, IV drug users, children under 4)

• ≥15 mm — Positive for persons with no known risk factors

Print tips:

• Print flat, no supports needed

• Use a dark filament for contrast against skin

• Verify hole dimensions with calipers after printing — adjust horizontal expansion in your slicer if needed

• Recommended layer height: 0.2 mm or finer

Note: This is a measurement aid, not a diagnostic device. Clinical interpretation of TST results should always be performed by a qualified healthcare provider considering the patient's full medical history and risk factors.