Recognize the indications for Isoniazid prophylaxis in a patient with a newly positive skin test for tuberculosis.
PPD conversion is a change from a negative PPD within the past 2 years to a positive PPD and is associated with a risk >3% per year of developing active DISEASE thus once disease is ruled out the patient should be given INH for 9 months.
If non compliant then weekly therapy for 12 months.
A change by more than 5 mm of induration is considered significant (examiners frequently trick people by saying erythema which has no significance).
There are a few other risk factors which are also associated with a higher risk of developing the disease. If anyone has these risk factors he/she should also be treated with INH for 9 months.
Risk factors include:
Steroid ingestion >15 mg/day
Total gastrectomy in the past
IV Illicit drug use
CXR with evidence of old tuberculosis (healed).
Children < 5 years age exposed to an infective case of TB should be treated too but for 3 months regardless of PPD result.
IF PREGNANT with risk factors-Treat.
Without risk factors-delay treatment until after delivery.
All HIV patients should be treated for 12 months if they are recent