In a 32-year-old patient with a history of intravenous drug use and hepatitis C who presents with new-onset edema and a low‑normal ejection fraction (50‑55%) on an otherwise normal echocardiogram, what laboratory tests should be ordered?

Laboratory Workup for New-Onset Edema in IVDU Patient with Hepatitis C

Order a comprehensive metabolic panel, complete blood count with platelets, urinalysis with urine protein-to-creatinine ratio, BNP or NT-proBNP, HIV screening, hepatitis C RNA PCR, and liver fibrosis assessment (FIB-4 or APRI score). 1, 2, 3

Core Laboratory Tests

Immediate Priority Labs

Renal and electrolyte assessment:

• Comprehensive metabolic panel (electrolytes, creatinine, BUN, albumin, bilirubin, ALT, AST)
• Serial monitoring of electrolytes and renal function is essential given the edema and borderline EF 1

Hematologic evaluation:

• Complete blood count with platelet count
• INR (international normalized ratio)
• These help assess liver synthetic function and guide fibrosis staging 2

Cardiac biomarkers:

• BNP or NT-proBNP measurement is Class I recommendation for establishing diagnosis and prognosis in heart failure, particularly useful with your patient's low-normal EF of 50-55% 1

Urinalysis:

• Urinalysis with microscopy
• Urine protein-to-creatinine ratio or 24-hour urine protein
• Critical to differentiate nephrotic syndrome (common in hepatitis C-associated glomerulonephritis) from other causes of edema

Hepatitis C-Specific Testing

Active infection confirmation:

• HCV RNA PCR testing to confirm active viremia (not just antibody status) 2, 4
• Do not wait for genotype results before proceeding with workup 3

Liver fibrosis assessment:

• Calculate FIB-4 score or APRI (AST-to-platelet ratio index) using the CBC and metabolic panel results 2, 3
• These noninvasive markers help determine cirrhosis risk, which dramatically changes management

High-Risk Population Screening

HIV testing:

• HIV screening is Class IIa recommendation for patients presenting with heart failure in selected populations 1
• Your patient with IVDU history absolutely qualifies for this screening
• HIV/HCV coinfection is common and affects treatment decisions 2

Thyroid function:

• TSH (thyroid-stimulating hormone) 1
• Both hypothyroidism and hyperthyroidism can cause edema and affect cardiac function

Critical Clinical Reasoning

The combination of IVDU, hepatitis C, and new edema raises three major diagnostic possibilities:

1. Hepatitis C-associated glomerulonephritis (membranoproliferative or membranous): The urinalysis and protein quantification are essential here
2. Early cirrhosis with portal hypertension: FIB-4/APRI scores and liver function tests will guide this
3. Infective endocarditis: While the echo was "otherwise normal," right-sided endocarditis (common in IVDU) may not always show obvious vegetations initially

Common Pitfalls to Avoid

• Don't assume hepatitis C antibody positivity means active infection - you need HCV RNA PCR 2, 4
• Don't overlook HIV coinfection - it's common in this population and changes hepatitis C treatment 2
• Don't skip urine studies - hepatitis C-associated kidney disease is a major cause of edema and often missed
• Don't delay fibrosis assessment - compensated cirrhosis can present subtly but requires different monitoring (varices, hepatocellular carcinoma surveillance) 4

Additional Considerations Based on Initial Results

If FIB-4 or APRI suggests advanced fibrosis (FIB-4 >3.25 or APRI >2.0), consider:

• Abdominal ultrasound with Doppler to assess for portal hypertension
• Alpha-fetoprotein for hepatocellular carcinoma screening 4

If proteinuria is significant (>500 mg/day), consider:

• Complement levels (C3, C4)
• Cryoglobulins (hepatitis C-associated cryoglobulinemia causes glomerulonephritis)
• Rheumatoid factor

The low-normal EF (50-55%) warrants the BNP/NT-proBNP measurement as this represents borderline HFmrEF territory and may indicate early cardiomyopathy (from alcohol, cocaine, or viral myocarditis - all relevant in IVDU population) 1.