Is PPD (Purified Protein Derivative) testing appropriate for a patient presenting with Upper Respiratory Infection (URI) symptoms?

PPD Testing for URI Symptoms: Not Appropriate as Routine Practice

PPD testing should not be performed routinely for patients presenting with simple upper respiratory infection (URI) symptoms, as URI symptoms alone do not constitute an indication for tuberculosis screening. 1

When TB Should Be Considered in Respiratory Illness

The critical distinction is between typical URI symptoms and TB-compatible symptoms. A diagnosis of TB should be considered for patients with a persistent cough lasting ≥3 weeks or other TB-specific symptoms including bloody sputum, night sweats, weight loss, anorexia, or fever. 1

Key Clinical Algorithm:

For typical URI symptoms (acute onset, <3 weeks duration):

• No PPD testing indicated 1
• Manage as routine URI

For persistent or TB-suggestive symptoms:

• Chest radiography should be the first-line investigation, not PPD testing 2
• PPD testing may be included as part of the diagnostic workup but should not delay imaging 1
• Never rely solely on negative PPD to exclude TB in symptomatic patients 2

Critical Pitfalls to Avoid

The most important caveat is that PPD testing has significant limitations in symptomatic patients:

• False-negative PPD results occur in 0-10% of immunocompromised patients 1, 2
• A negative PPD does not exclude active tuberculosis, particularly in symptomatic individuals 2
• Do not delay chest radiography while waiting for PPD results in symptomatic patients 2

Risk-Based Approach

PPD testing is appropriate for asymptomatic screening in specific high-risk populations, not for diagnostic evaluation of acute respiratory symptoms:

• Healthcare workers with TB exposure 1
• Recent close contacts of active TB cases 1
• Immunosuppressed patients (HIV, biologics, chronic steroids) 1
• Immigrants from high TB burden countries 1
• Residents of congregate settings 3

Proper Diagnostic Sequence for Suspected TB

When TB is clinically suspected based on symptom duration and character:

1. Order chest radiography immediately - look for upper lobe infiltrates, cavitation, hilar/mediastinal adenopathy, or Ghon complex 1, 2
2. Collect sputum for AFB smear and culture if radiograph is abnormal 1
3. Implement respiratory isolation pending results 1
4. PPD testing may supplement but should not replace this approach 1

Patients from endemic regions require chest radiography even with negative PPD if symptomatic, due to increased pre-test probability of TB. 2

The evidence consistently shows that chest radiography has higher sensitivity than PPD testing for detecting active TB and should be prioritized in symptomatic patients. 1 PPD testing is fundamentally a screening tool for latent infection in asymptomatic individuals, not a diagnostic test for active disease in symptomatic patients.