What lab tests should be included in a complete lab order?

Complete Laboratory Order

For a general "complete lab order" in routine clinical practice, order a Complete Blood Count (CBC), Comprehensive Metabolic Panel (CMP), and consider adding Thyroid-Stimulating Hormone (TSH) based on clinical context. 1

Core Laboratory Components

Essential Tests for Most Clinical Scenarios

• Complete Blood Count (CBC) with differential should be included to assess for anemia, infection, thrombocytopenia, and other hematologic abnormalities 2, 1
• Comprehensive Metabolic Panel (CMP) provides critical information including electrolytes (sodium, potassium, chloride, bicarbonate), kidney function (BUN, creatinine), liver function (AST, ALT, alkaline phosphatase, bilirubin), glucose, calcium, and albumin 1, 2
• Thyroid-Stimulating Hormone (TSH) is recommended for initial evaluation in many clinical contexts, particularly when screening for metabolic causes of symptoms 1, 2

Additional Baseline Testing When Clinically Indicated

• Liver function tests (LFTs) including AST, ALT, alkaline phosphatase, and bilirubin are essential when hepatic disease is suspected or before initiating hepatotoxic medications 2
• Coagulation studies including PT/INR, aPTT, fibrinogen, and D-dimer should be added when evaluating bleeding risk, coagulopathy, or before invasive procedures 2, 3
• Urinalysis provides screening for renal disease, infection, and metabolic abnormalities 2

Context-Specific Laboratory Additions

For Medication Monitoring

• Renal function tests (BUN, creatinine) are particularly important before starting methotrexate, sulfasalazine, or NSAIDs 2
• Lipid profiles should be obtained as baseline before initiating tocilizumab or tofacitinib 2
• Monitoring frequency varies by medication: NSAIDs require CBC, LFTs, and renal function every 6-12 months, while methotrexate requires monitoring within 1-2 months of initiation and every 3-4 months thereafter 2

For Specific Clinical Presentations

• Tumor lysis syndrome panel (LDH, uric acid, potassium, phosphate, calcium) is essential when evaluating patients with high tumor burden or hyperleukocytosis 2
• DIC panel (D-dimer, fibrinogen, PT, PTT) should be ordered when disseminated intravascular coagulation is suspected 2
• Pregnancy testing must be performed in all females of childbearing potential before initiating teratogenic medications or certain procedures 2

Important Clinical Considerations

Timing and Interpretation

• Baseline laboratory testing is recommended prior to treatment onset for medications with known toxicity profiles 2
• Coagulation studies (PT/INR, aPTT) can be misleading in certain contexts—prolonged values may paradoxically indicate thrombosis risk in cirrhosis rather than bleeding risk 3
• Protein C, Protein S, and Antithrombin III levels are consumed during acute thrombosis and will be falsely low; ideally test 2-4 weeks after an acute thrombotic event 3

Common Pitfalls to Avoid

• Avoid reflexive coagulation panels without clinical indication—studies show only 8% of coagulation panel orders are clinically indicated based on patient history, with fibrinogen being normal in 98% of cases 4
• A normal PT or aPTT does NOT exclude the presence of direct oral anticoagulants (DOACs) such as dabigatran, rivaroxaban, or apixaban 5
• Do not rely on PT/aPTT alone to assess bleeding risk—these tests primarily evaluate specific coagulation pathways and may not reflect overall hemostatic function 5, 6

Special Populations

• For patients with intellectual disabilities being evaluated for cognitive decline, include CBC, comprehensive metabolic panel, thyroid function tests, B12, folate, and liver function tests 2
• Pediatric patients undergoing chemotherapy require more extensive monitoring including tumor lysis panels and fertility preservation counseling before treatment initiation 2
• Patients undergoing ECT require CBC, differential white blood cell count, thyroid function tests, liver function tests, urinalysis and toxicology screen, ECG, and pregnancy testing in all females 2