A 52-year-old man comes to the office for a follow-up visit. He had a pre-employment tuberculin skin test done 3 days ago, and had a skin reaction with 16 mm of induration. He has not had any cough, fever, weight loss, night sweats, or recent exposure to patients with tuberculosis. He has a 40-pack-year history of smoking and continues to smoke heavily. He immigrated from South Korea to the United States about 8 years ago. He had BCG vaccination as a child but never had a tuberculin skin test done in the past. A chest x-ray is ordered and shows right upper lobe fibrosis without signs of active tuberculosis. Which of the following is the most appropriate next step in the management of this patient?

Question

A 52-year-old man comes to the office for a follow-up visit.  He had a pre-employment tuberculin skin test done 3 days ago, and had a skin reaction with 16 mm of induration.  He has not had any cough, fever, weight loss, night sweats, or recent exposure to patients with tuberculosis.  He has a 40-pack-year history of smoking and continues to smoke heavily.  He immigrated from South Korea to the United States about 8 years ago.  He had BCG vaccination as a child but never had a tuberculin skin test done in the past.  A chest x-ray is ordered and shows right upper lobe fibrosis without signs of active tuberculosis.  Which of the following is the most appropriate next step in the management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bfc6_30b7_8f63_f979ce81e690_MD0005_00 Given that this patient was born in South Korea, which has a relatively high incidence of tuberculosis, a 10 mm of induration cutoff for the tuberculin skin test would be most appropriate. This patient's 16 mm area of induration would therefore count as a positive test. A confounding factor in this case is the patient's prior BCG vaccination. Induration from BCG rarely exceeds 15 mm, and significantly decreases 15 years after it is received. Interferon gamma release assays can be used to distinguish a true positive tuberculin skin test from prior BCG vaccination. A chest x-ray is also a reasonable step to differentiate the 2 entities, with this patient's upper lobe fibrosis strongly suggestive of latent tuberculosis. While there are no radiographic signs of active infection in this patient, the presence of active tuberculosis cannot be entirely excluded radiographically and correlation with the patient's symptoms is needed. Ancillary tests such as sputum culture may be needed before determining that the patient has no active tuberculosis. Given the radiographic findings and absence of clinical symptoms in this patient, latent tuberculosis is most likely. Treatment is still indicated for latent tuberculosis since the infection can become reactivated should the patient become immunocompromised. Several rifamycin-based regimens taken for 3-4 months (eg, daily rifampin for 4 months; daily isoniazid and rifampin for 3 months) are recommended unless there are contraindications (eg, drug-drug interactions). Longer courses are not necessary and may increase risk of hepatotoxicity (Choices D and E). (Choice A) This patient needs treatment for his latent tuberculosis otherwise he may develop reactivation should he become immunocompromised. (Choice B) Given that the patient has no evidence of active infection it is unlikely that the chest x-ray will change in a month. If there is concern for active infection then the patient's sputum should be cultured for acid fast bacilli. Educational objective: Prior BCG vaccination should rarely cause more than 15 mm induration with tuberculin skin testing. The effect of BCG vaccination on induration decreases significantly 15 years after the vaccine is received. Rifamycin-based treatment regimens for 3-4 months are recommended for patients with latent tuberculosis. References: A meta-analysis of the effect of Bacille Calmette Guérin vaccination on tuberculin skin test measurements. (http://www.ncbi.nlm.nih.gov/pubmed/12200526) Identification and management of latent tuberculosis infection. (http://www.ncbi.nlm.nih.gov/pubmed/19496388)

A 52-Year-Old Man Comes to the Office for a Follow-Up