Baseline Laboratory Tests Before Starting Rifampin
For active tuberculosis treatment, obtain baseline measurements of hepatic enzymes (ALT, AST, bilirubin, alkaline phosphatase), serum creatinine, platelet count, HIV testing, and hepatitis B/C screening. 1
Essential Baseline Tests for Active TB Treatment
Hepatic Function Panel
- ALT (alanine aminotransferase)
- AST (aspartate aminotransferase)
- Bilirubin
- Alkaline phosphatase 1
These liver function tests are critical because rifampin can cause hepatotoxicity, particularly when combined with other anti-TB medications like isoniazid and pyrazinamide. 2
Renal Function
- Serum creatinine 1
Hematologic Tests
- Platelet count (or complete blood count) 1
Infectious Disease Screening
- HIV testing - mandatory for all TB patients 1
- CD4 count and HIV RNA load if HIV-positive 1
- Hepatitis B and C screening - particularly important for patients with risk factors (injection drug use, foreign birth in Asia or Africa, HIV infection) 1
Additional Metabolic Tests (for specific regimens)
- Potassium, calcium, and magnesium - required when using rifapentine-moxifloxacin regimens 1
Other Baseline Assessments
- Diabetes screening 1
- Pregnancy testing for persons who might become pregnant 1
- Weight for proper drug dosing 1
Baseline Tests for Latent TB Infection (LTBI) Treatment
Baseline laboratory testing is NOT routinely indicated for all patients starting rifampin monotherapy for LTBI. 1
When Baseline Testing IS Required for LTBI:
Obtain baseline AST/ALT and bilirubin if the patient has: 1
- HIV infection
- Pregnancy or immediate postpartum period (within 3 months of delivery)
- History of chronic liver disease (hepatitis B or C, alcoholic hepatitis, cirrhosis)
- Regular alcohol use
- Clinical suspicion of liver disorder on initial evaluation
- Taking other potentially hepatotoxic medications
- Previous drug-induced liver injury
Baseline testing is not routinely indicated based solely on age >35 years, though it may be considered individually for patients on multiple medications for chronic conditions. 1
Critical Clinical Considerations
Hepatotoxicity Risk
When rifampin is combined with other hepatotoxic medications (particularly isoniazid), the risk of hepatotoxicity increases substantially. 2 Patients with baseline bilirubin exceeding 50 μmol/L are at higher risk for rifampin accumulation and may require dose reduction. 3
Drug Interactions
Rifampin is a potent inducer of drug-metabolizing enzymes (CYP1A2, 2B6, 2C8, 2C9, 2C19, 3A4) and transporters (P-glycoprotein, MRP2), which can significantly alter the metabolism of concomitant medications. 2, 4 A detailed medication history is essential before starting rifampin.
Monitoring During Treatment
For active TB, follow-up liver function tests are only required if: 1
- Baseline abnormalities exist
- Symptoms of hepatotoxicity develop
- Patient has chronic alcohol use, viral hepatitis, or HIV infection
- Patient takes other hepatotoxic medications
For LTBI with rifampin monotherapy, routine laboratory monitoring is indicated only for patients with baseline abnormalities or those at increased risk for hepatic disease. 1