The tuberculin skin test (TST) form documents the administration and subsequent biological reaction to the Purified Protein Derivative (PPD) solution. Accurate, standardized documentation is necessary for proper patient care and public health tracking of tuberculosis exposure. Failure to complete the form precisely can compromise the test’s validity and lead to misinterpretation of a patient’s infection status.
Documenting the Test Administration Details
The initial section of the form captures the logistics of the injection, which must be recorded immediately after the procedure. Patient information, including full name, date of birth, and medical record number, must be confirmed and accurately transcribed to ensure the record is linked to the correct individual. This step prevents mix-ups that could affect a patient’s long-term health management.
Documentation must include the exact date and time the PPD solution was administered, along with the precise anatomical injection site, such as the volar aspect of the left forearm. Recording the site is important because skin thickness varies, and future tests should be performed in a similar location. The healthcare professional who performed the injection must sign or initial the form to certify the administration details.
The form dedicates a section to the tuberculin solution, typically 0.1 mL of PPD containing five tuberculin units (TU). This requires recording the manufacturer, the product’s name (e.g., TUBERSOL), and the expiration date found on the vial. The lot number, a unique alphanumeric identifier assigned to a specific batch of PPD, is important for quality assurance and traceability. If a batch is later found to have potency issues, the lot number allows public health officials to rapidly identify and follow up with all exposed individuals.
Recording the Reading and Measurement
The TST reaction must be measured by a trained healthcare professional within a window of 48 to 72 hours after the injection. If the reading is not performed within this timeframe, the test is considered invalid and must be repeated. The form requires documentation of the exact date and time the reading occurred.
The professional must visually inspect the injection site and then use palpation to determine the presence and size of induration, which is the firm, raised swelling caused by a delayed hypersensitivity reaction. Induration must be differentiated from erythema (redness), as redness has no diagnostic significance and should be disregarded. The measurement technique involves using a flexible plastic ruler or caliper to measure the diameter of the induration only.
The induration is measured across the widest diameter of the firm area, perpendicular to the long axis of the forearm. The measurement must be recorded in exact millimeters (mm), not simply as a qualitative description. If no induration is present, the result must be documented as “0 mm,” avoiding the use of only the word “negative” at this stage of the process.
Interpreting and Certifying the Results
The final step on the form is the clinical interpretation, which converts the physical measurement (in mm) into a final classification of Positive or Negative. This interpretation cannot be made based solely on the measurement because the threshold for a positive result depends on the patient’s individual risk factors for tuberculosis infection. The healthcare provider must use established guidelines to make this determination.
The threshold for a positive result depends on the patient’s individual risk factors. For the highest-risk individuals (e.g., those with HIV or recent close contact), five millimeters or more is considered positive. A threshold of ten millimeters or more is used for moderate-risk factors, such as recent immigrants or those with certain medical conditions. The lowest-risk group, who have no known risk factors, requires an induration of fifteen millimeters or more to be classified as positive.
The form must document the final interpretation based on these risk-stratified thresholds. The professional who performs the reading and interpretation must sign the form and provide credentials, certifying the accuracy of the record. This certification ensures the documentation is complete and actionable for the patient’s medical management.