What laboratory tests are recommended for patients on methotrexate (MTX), including those with a history of liver disease or at high risk of liver toxicity?

Laboratory Monitoring for Methotrexate Therapy

All patients on methotrexate require baseline assessment with CBC with differential and platelet count, comprehensive metabolic panel, liver function tests, hepatitis B and C serologies, non-invasive liver fibrosis assessment, chest X-ray, and pregnancy test in women of childbearing potential, followed by CBC, liver function tests, and renal function tests every 2-4 weeks initially, then monthly for the first 6 months, and every 1-3 months thereafter. 1, 2, 3

Baseline Laboratory Assessment

Before initiating methotrexate, obtain the following tests:

• Complete blood count with differential and platelet count 1, 2, 3
• Comprehensive metabolic panel including liver function tests (ALT, AST, alkaline phosphatase, albumin, bilirubin) and renal function tests (creatinine, BUN) 1, 2, 3
• Hepatitis B and C serologies 1, 2
• Non-invasive liver fibrosis assessment (FIB-4 Index, Fibrosure, Fibrometer, or Hepascore) 1
• Chest X-ray to establish baseline pulmonary status 1, 2
• Pregnancy test in women of childbearing potential 1, 2

Baseline liver biopsy is NOT recommended, regardless of risk factors for hepatotoxicity. 1, 3

Standard Monitoring Schedule

Initial Phase (First 6 Months)

• CBC with differential, liver function tests, and renal function tests every 2-4 weeks during the first 2-4 months 1, 2
• Monthly monitoring for months 3-6 1, 2

Maintenance Phase (After 6 Months)

• CBC, liver function tests, and renal function tests every 1-3 months 1, 2, 4
• The American College of Rheumatology recommends monitoring every 3-4 months after initial stabilization in patients without organ dysfunction 1

After Dose Increases

• Return to every 2-4 weeks monitoring for at least 6 weeks after any dose adjustment, as pancytopenia can occur as late as 6 weeks post-adjustment 1

Intensified Monitoring for High-Risk Patients

Patients with pre-existing renal or liver disease require more frequent monitoring:

• CBC, liver function tests, and renal function tests every 2-4 weeks initially 1
• Monthly for the first 6 months 1
• Every 1-3 months thereafter 1
• Consider a test dose before full therapeutic dosing in patients with decreased kidney function 1

Risk factors requiring enhanced monitoring include: 1, 2, 5

• Obesity (BMI >28 kg/m²)
• Diabetes mellitus
• Chronic liver disease or history of alcohol use
• Untreated hyperlipidemia
• Renal impairment
• Advanced age (>70 years)
• Hypoalbuminemia

Critical Monitoring Parameters and Action Thresholds

Hematologic Parameters

Hold methotrexate if: 1

• White blood cell count <3.0 × 10⁹/L
• Absolute neutrophil count <1.0-2.0 × 10⁹/L
• Platelet count <100 × 10⁹/L
• Mean corpuscular volume >105 fL

Liver Function Tests

Important timing consideration: Do not check liver function tests within 2 days of methotrexate dose, as transient elevations may occur 1, 2, 3

Hold methotrexate if: 1, 4

• ALT/AST persistently >2-3 times upper limit of normal
• Persistent abnormalities defined as elevations in AST in 5 of 9 determinations within a 12-month interval (or 6 of 12 if tested monthly)
• Serum albumin decreases below normal range

Discontinue methotrexate if: 1

• ALT/AST >5 times upper limit of normal
• ALT/AST >3 times upper limit of normal despite dose reduction

Additional Liver Assessment for High-Risk Patients

For patients with obesity (BMI >28 kg/m²), diabetes, hyperlipidemia, or alcohol consumption >14 drinks/week: 1, 2

• Perform non-invasive fibrosis assessment with FIB-4 Index
• If results suggest greater than minimal fibrosis, refer to gastroenterology/hepatology for vibration-controlled transient elastography (FibroScan)

Mandatory Folic Acid Supplementation

All patients on methotrexate must receive folic acid supplementation: 1, 2, 6

• Dose: 1-5 mg daily, taken 6 days per week (not on the day of methotrexate administration)
• This reduces gastrointestinal, hepatic, and hematologic toxicity without compromising efficacy
• Lack of folate supplementation is a major preventable risk factor for methotrexate toxicity 6, 5

Common Pitfalls to Avoid

• Do not check liver function tests within 2 days after methotrexate dose - transient elevations are expected and do not indicate true hepatotoxicity 1, 2
• Do not perform routine baseline liver biopsies - these are not recommended regardless of risk factors 1, 3
• Do not ignore persistent liver enzyme elevations - these require dose reduction or discontinuation, not just continued monitoring 1, 4
• Do not forget to increase monitoring frequency after dose adjustments - return to every 2-4 weeks for at least 6 weeks 1
• Do not overlook drug interactions - NSAIDs, trimethoprim-sulfamethoxazole, and penicillins can significantly increase methotrexate toxicity 1, 3

When to Hold or Discontinue Methotrexate

Temporarily hold methotrexate for: 1

• Acute intercurrent illness or active infection
• Significant elevation in liver function tests (ALT/AST >2-3× ULN)
• Hematologic abnormalities as outlined above

Permanently discontinue methotrexate for: 1

• Persistent liver function test abnormalities despite dose reduction
• ALT/AST >5× upper limit of normal
• Development of pulmonary symptoms
• Severe pancytopenia or bone marrow suppression