What is the next step for a patient with a positive Purified Protein Derivative (PPD) test result?

Management of a Patient with a Positive PPD Test

The next step for a patient with a positive Purified Protein Derivative (PPD) test is to promptly perform a clinical evaluation and chest radiograph to rule out active tuberculosis. 1, 2

Initial Evaluation Process

• All individuals with a newly recognized positive PPD test result should undergo immediate clinical examination and chest radiography to exclude active tuberculosis disease 1, 2
• The clinical evaluation should focus on symptoms suggestive of TB such as cough, fever, night sweats, weight loss, and hemoptysis 1
• If the history, clinical examination, or chest radiograph is compatible with active TB, additional diagnostic tests should be performed, including sputum collection for AFB smear and culture 1
• Patients with symptoms compatible with TB should be excluded from the workplace or school until either active TB is ruled out or the patient is receiving treatment and determined to be non-infectious 1

Interpretation of Chest Radiograph

• Radiographic abnormalities suggestive of active TB include upper-lobe infiltration (particularly with cavitation), patchy or nodular infiltrates in the apical or subapical posterior upper lobes 1
• If the chest radiograph is negative and the patient is asymptomatic, this indicates latent TB infection rather than active disease 2
• Repeat chest radiographs are not needed for PPD-positive individuals with a normal initial chest radiograph unless symptoms develop that could be attributed to TB 1
• In children and adolescents, the prevalence of abnormal chest radiograph findings after a positive PPD is very low (approximately 1%) 3

Management Based on Findings

If Active TB is Ruled Out (Latent TB Infection):

• Evaluate the patient for preventive therapy according to published guidelines 1, 2

• Treatment options for latent TB infection include:

  • Isoniazid 300 mg daily for 9 months (preferred regimen) 2, 4, 5
  • Rifampin 600 mg daily for 4 months (alternative regimen) 2, 4
  • Rifampin and isoniazid daily for 3 months 5

• Special considerations for specific populations:

  • HIV-infected persons should receive at least 12 months of preventive therapy 4
  • Patients with fibrotic pulmonary lesions consistent with healed TB should receive 12 months of isoniazid or 4 months of isoniazid and rifampin 4
  • Patients on immunosuppressive therapy or planning to start biologics should receive treatment for latent TB infection before continuing or initiating biologic therapy 2, 6

If Active TB is Diagnosed:

• The patient should be excluded from the workplace or school until they are non-infectious 1
• Standard treatment for active TB typically consists of isoniazid, rifampicin, pyrazinamide, and etambutol for the first 2 months, followed by isoniazid and rifampicin for at least 4 additional months 7
• Before returning to work/school, documentation should confirm that the patient is receiving adequate therapy, cough has resolved, and three consecutive negative sputum smears have been collected on different days 1

Monitoring During Treatment

• Liver function tests should be monitored every 2-4 weeks during treatment 1, 2
• Patients should be educated about symptoms of hepatotoxicity (nausea, vomiting, jaundice) 2
• Patients receiving isoniazid should also receive pyridoxine (vitamin B6) to prevent peripheral neuropathy, especially HIV-infected persons 2

Common Pitfalls and Considerations

• The interpretation of PPD induration depends on the patient's risk factors:

  • ≥5 mm is considered positive for HIV-infected persons, recent contacts of TB cases, and persons with immunosuppression 2, 8
  • ≥10 mm is considered positive for persons at increased risk of TB 8
  • ≥15 mm is considered positive for persons with no known risk factors 8

• BCG vaccination history should not affect the interpretation of a positive PPD test in adults, particularly if the vaccination was administered during childhood 1, 6

• Anergy (lack of reaction to skin tests) is common in HIV-infected patients (63%) and can complicate the interpretation of negative PPD results 9

• In patients with autoimmune diseases planning to start TNF-alpha inhibitors, TB screening is essential, and if LTBI is diagnosed, TB chemoprophylaxis should be started at least one month before initiating TNF-alpha therapy 6