Which baseline laboratory tests should be obtained before initiating ustekinumab (Stelara) for a patient with psoriasis?

Baseline Laboratory Testing for Stelara (Ustekinumab) in Psoriasis

Before starting Stelara for psoriasis, you must obtain: CBC with differential, complete metabolic profile (CMP), tuberculosis screening (PPD, QuantiFERON Gold, or T-Spot), and hepatitis B and C serologies (HBsAg, anti-HBs antibody, anti-HBc antibody, and HCV antibody). 1

Required Baseline Labs

The 2019 Joint AAD-NPF Guidelines provide clear baseline monitoring requirements for ustekinumab:

Mandatory Tests

• CBC with differential - screens for baseline hematologic abnormalities 1
• Complete metabolic profile (CMP) - establishes baseline liver and kidney function 1
• Tuberculosis screening - pretreatment test using PPD, QuantiFERON Gold, or T-Spot is required 1
• Hepatitis B panel - HB surface antigen, anti-HB surface antibody, anti-HB core antibody 1
• Hepatitis C antibody 1

Discretionary Testing

• HIV testing - recommended at the treating practitioner's discretion based on patient-specific risk factors 1
• Chest radiograph - only if TB test is positive 1

Important Clinical Context

Why These Labs Matter

Tuberculosis screening is critical because IL-12/23 inhibition can theoretically impair immunity to Mycobacterium tuberculosis, though serious opportunistic infections including TB are rarely observed with ustekinumab in clinical practice 1. If latent TB is identified, concurrent isoniazid prophylaxis is well-tolerated and prevents reactivation 2.

Hepatitis B screening is essential because patients with active hepatitis B require evaluation by an appropriate specialist and may need concomitant antiviral therapy before starting ustekinumab 1. Patients with resolved hepatitis B infection (positive core antibody) don't need specialist follow-up but require ongoing monitoring due to reactivation risk 1.

Hepatitis C can be treated with ustekinumab, but screening establishes baseline status 1.

Key Distinction from Other Biologics

Unlike TNF inhibitors (especially infliximab), ustekinumab does NOT require routine ongoing monitoring of CBC and liver function tests - these are obtained at baseline but subsequent monitoring is not supported by evidence and is left to physician discretion 1. This represents a significant practical advantage over other systemic therapies.

Common Pitfalls to Avoid

1. Don't order unnecessary ongoing labs - The guidelines explicitly state that CBC and CMP monitoring after baseline is "not supported by evidence" for ustekinumab 1. This differs from methotrexate or infliximab where regular monitoring is required.

2. Don't delay treatment for mildly elevated liver enzymes - Recent real-world evidence shows that patients with elevated baseline liver function tests actually experience improvement in these values during ustekinumab therapy, and elevated LFTs should not be considered a contraindication 3.

3. Don't skip TB screening - Even though serious infections are rare with ustekinumab compared to TNF inhibitors, TB screening remains mandatory 1.

4. Consider HIV testing thoughtfully - While not universally required, HIV testing should be obtained in patients with risk factors. HIV-positive patients can receive ustekinumab if they're on effective HAART with normalized CD4 counts and undetectable viral load 1.

Practical Workflow

1. Order baseline labs: CBC, CMP, TB test (QuantiFERON or PPD), HBV panel, HCV antibody
2. Consider HIV test based on risk factors
3. If TB test positive → obtain chest X-ray and refer to infectious disease
4. If HBsAg positive → refer to hepatology/infectious disease before starting therapy
5. If all screening appropriate → initiate ustekinumab without need for routine ongoing laboratory monitoring