What should the cut-off reading for a positive tuberculosis skin test (aka PPD) be for someone with hepatitis C?

Bottom line: The cutoff for a positive PPD reading in patients with hepatitis C has not been well studied, and the PPD should be interpreted with caution.
Summary: Evidence is limited or nonexistent as to sensitivity, specificity, and positive cutoff PPD readings for patients with TB and hepatitis C. For interpretation of PPD skin test in adults, DynaMed provides this guidance on readings in adults (a separate section is provided for guidance in children and adolescents):
induration ≥ 15 mm considered positive in persons with no risk factors for tuberculosis (TB)
induration ≥ 10 mm considered positive in
o    injection drug users
o    persons with high-risk clinical conditions
– silicosis
– diabetes mellitus
– chronic renal failure
– some hematologic disorders (for example, leukemias and lymphomas)
– other specific malignancies (for example, carcinoma of the head or neck and lung)
– weight loss ≥ 10% or more of ideal body weight
– gastrectomy
– jejunoileal bypass
o    children < 4 years old
o    infants, children, and adolescents exposed to adults at high risk
o    recent immigrants (within previous 5 years) from high-prevalence countries
o    persons from medically underserved, low-income populations
o    residents and employees of high-risk congregate settings (prisons, nursing homes and other long-term care facilities, residential facilities for patients with Acquired Immune Deficiency Syndrome [AIDS], homeless shelters); ≥ 15 mm induration considered positive for employees who are otherwise at low risk and are tested at start of employment
o    mycobacteriology laboratory personnel (Active Tuberculosis > Diagnosis > Other Diagnostic Testing > Tuberculin Skin Testing (TST) > Interpretation of PPD Skin Test. In DynaMed).


About Lisa

I have been a Clinical Informationist (aka Medical Librarian) for Emory University since September 2013. Prior to that, I was a Medical Librarian for Lincoln Memorial University (LMU) from March 2007 to August 2013 and served its DeBusk College of Osteopathic Medicine, Caylor School of Nursing, and allied health programs. From January 2002 - March 2007, I served the Medical Assisting (MA), Occupational Therapy Assistant, Physical Therapy Assistant, Radiologic Technologist, and Nursing programs at South College in Knoxville, Tennessee. I graduated from The University of Tennessee School of Information Sciences with a Master of Science degree in December 2000.
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