A Medical Assistant (MA) is an allied health professional who performs administrative and clinical tasks under the supervision of a licensed practitioner. A common clinical task is screening for exposure to Mycobacterium tuberculosis, the bacterium that causes tuberculosis. This screening often involves the Tuberculin Skin Test (TST), also known as the Mantoux test. Determining if an MA can “read” this test requires distinguishing between the technical measurement of the reaction and the clinical judgment needed for interpretation.
Understanding the Tuberculin Skin Test Procedure
The TST is performed by injecting a small amount of purified protein derivative (PPD) tuberculin just under the top layer of skin on the inner forearm (an intradermal injection). If a person has been infected with TB bacteria, their immune system mounts a delayed-type hypersensitivity reaction to the PPD antigen. This reaction site must be physically assessed by a trained healthcare worker between 48 and 72 hours after the injection.
The physical assessment involves measuring the diameter of the induration. Induration is the palpable, raised, and hardened area at the injection site. Measurement must focus only on this firm swelling in millimeters, not the surrounding redness (erythema). Accurate technical skill is required to identify the margins of the hardened area for a precise measurement.
Medical Assistant Scope: Measuring Induration vs. Clinical Interpretation
The MA’s role in the TST process involves two distinct parts: technical measurement and final clinical interpretation. Medical Assistants who have received specific, documented training and demonstrated competency are often permitted to perform the physical measurement of the induration. This task is considered a technical function performed under the direct supervision of a licensed provider.
The physical measurement (e.g., 5 mm or 10 mm) is recorded by the MA in the patient’s chart. However, MAs are generally prohibited from performing the final interpretation of that measurement. Interpretation requires the clinician to determine if the measured induration is a positive, negative, or inconclusive result based on the patient’s individual risk factors.
For example, a 5-millimeter measurement may be positive for an immunocompromised patient but negative for a healthy individual. This determination requires clinical judgment, which is legally reserved for licensed practitioners (e.g., a physician, nurse practitioner, or physician assistant). Professional guidelines stress that MAs should not interpret any clinical or diagnostic test, including the TST result.
State-Level Regulation and Delegation
Authority regarding whether an MA can measure a TST reaction rests with the state’s board of medical examiners or nursing, and the employing facility’s policies. Since the MA role is not uniformly licensed across the United States, the scope of practice varies widely based on local law. In many states, MAs are considered unlicensed personnel, meaning they can only perform tasks explicitly delegated by a licensed healthcare provider.
Delegation protocols usually require the MA to hold a current certification, such as Certified Medical Assistant (CMA) or Registered Medical Assistant (RMA). They must also have completed documented, hands-on training for the TST procedure. The delegating practitioner remains legally responsible for the MA’s performance and the final interpretation of the result. Therefore, MAs measuring induration under delegation must adhere to the specific protocols and limitations established by their state and supervising clinician.