A tine test is a skin test for tuberculosis (TB) that uses a small device with multiple metal prongs to press tuberculin, a protein derived from TB bacteria, into the top layer of your skin. It was once widely used as a quick screening tool but has largely been replaced by the Mantoux test, which injects a measured dose of tuberculin under the skin with a needle and is considered more reliable.
How the Tine Test Works
The device looks like a small disc or handle with four to six short metal prongs (called tines) on one end. These prongs are either pre-coated with dried tuberculin reagent or dipped in liquid tuberculin just before use. The clinician presses the device firmly against the inner forearm for a second or two, and the prongs create tiny punctures that deliver the tuberculin into the skin. It uses a substance called Old Tuberculin, which is different from the purified protein derivative (PPD) used in the Mantoux method.
The test works by triggering an immune response. If your body has previously encountered TB bacteria (through infection or vaccination), immune cells in your skin recognize the tuberculin and mount a localized reaction, producing a firm, raised bump called induration. You return to have the site read 48 to 72 hours later.
Reading the Results
A healthcare provider reads the test by feeling the forearm for induration, not just looking for redness. What matters is the diameter of the firm, raised area, measured in millimeters. If there’s no induration at all, the result is recorded as 0 mm.
The threshold for a positive result depends on who’s being tested. For people with HIV or children who are severely malnourished, induration of 5 mm or more is considered positive. For most other people, 10 mm or more counts as positive. These cutoffs reflect the fact that people with weakened immune systems may produce a smaller reaction even when they’re truly infected.
A positive result does not mean you have active TB disease. It means your immune system has been exposed to TB bacteria at some point, either through actual infection or, in some cases, through the BCG vaccine given in many countries outside the United States.
Why the Tine Test Was Replaced
The tine test fell out of favor in most developed countries during the 1970s and 1980s because of a high rate of false negative results. Studies found that a significant number of people who tested positive on the more precise Mantoux method came back negative on the tine test. The British Thoracic Association specifically concluded that the tine test was unsuitable for epidemiological use because so many people with confirmed positive Mantoux results showed negative tine results.
The core problem is dosage control. With the Mantoux test, a clinician injects a precise, standardized amount of tuberculin (0.1 mL) into the skin with a needle. With the tine test, the amount of tuberculin delivered depends on how firmly the device is pressed, how much reagent remains on the prongs, and individual skin characteristics. This variability made results less consistent and harder to compare across populations.
That said, the tine test wasn’t dramatically less accurate in all settings. A study comparing both methods in over 1,500 children investigated for TB found 87.3% agreement between the two tests. Among 173 children with culture-confirmed TB, the tine test actually identified a slightly higher percentage of cases (54.9%) than the Mantoux test (49.1%). Still, the Mantoux became the standard because its results are more reproducible and easier to interpret against established clinical guidelines.
The BCG Vaccine Complication
One limitation shared by both the tine test and the Mantoux test is that neither can reliably distinguish between a reaction caused by actual TB infection and one caused by the BCG vaccine. BCG is a TB vaccine given routinely in many parts of the world, particularly in countries where TB is common. According to the CDC, there is no reliable way to tell these two causes apart based on a skin test alone.
People who received multiple BCG doses tend to have stronger and longer-lasting skin test reactions. BCG-related reactivity typically fades over time, but repeated skin testing can actually boost it, making the problem worse. This is one reason TB blood tests (which measure the immune response in a blood sample rather than in the skin) are often preferred for people who’ve been vaccinated with BCG.
What’s Used Today
If your doctor orders a TB skin test today, you’ll almost certainly receive the Mantoux test. A small needle injects a precise dose of purified tuberculin just under the skin of your inner forearm, creating a small, pale bump. You return in 48 to 72 hours to have the site measured. The process is quick, and the injection feels like a brief pinch.
The other modern option is a TB blood test, sometimes called an interferon-gamma release assay. A single blood draw is all that’s needed, with no return visit required. These tests are not affected by prior BCG vaccination, which makes them especially useful for people born in countries where BCG is routine. Your provider will choose based on your risk factors, vaccination history, and the reason for testing.