Should I order blood labs for this patient?

Should Blood Labs Be Ordered?

Yes, order blood labs when they will answer a specific clinical question or change management, but avoid routine daily testing without clinical indication. 1

Core Principle: Test Only When Clinically Indicated

The American Thoracic Society/American Association of Critical-Care Nurses/American College of Chest Physicians/Society of Critical Care Medicine explicitly recommends not ordering diagnostic tests at regular intervals (such as daily), but rather in response to specific clinical questions. 1 Routine ordering of tests increases healthcare costs, does not benefit patients, and may harm them through iatrogenic anemia from unnecessary phlebotomy and aggressive work-up of incidental findings. 1

Essential Blood Tests to Consider Based on Clinical Context

For Suspected Cardiac Conditions

• Troponin I or T (high-sensitivity assays preferred) to rule out acute myocardial injury if clinical or ECG assessment suggests acute coronary syndrome rather than chronic coronary syndrome 1
• Lipid profile including LDL-C for risk stratification 1
• Creatinine with estimation of renal function as renal dysfunction increases likelihood of coronary artery disease and impacts prognosis 1
• HbA1c and/or fasting plasma glucose for glycemic status assessment 1
• Full blood count (including hemoglobin) as anemia can cause ischemia 1
• Thyroid function at least once in patients with suspected chronic coronary syndrome 1

For Suspected Infection or Sepsis

• Complete blood count to assess for systemic infection 1
• Serum creatinine and electrolytes to assess patient status 1
• Inflammatory markers (C-reactive protein, procalcitonin) for early diagnosis 1
• Blood gas analysis to evaluate severity 1
• Serum glucose, hemoglobin A1c, and urine ketones to investigate undetected diabetes mellitus, particularly in suspected Fournier's gangrene 1

For Suspected Bleeding or Coagulation Disorders

• Complete blood count including platelets systematically or according to clinical context 1
• Coagulation studies (PT, INR, aPTT) to assess clotting function 1, 2
• Hemoglobin and hematocrit to determine severity of bleeding 1
• Blood typing and cross-matching in cases of severe bleeding 1

For Perioperative Assessment

• Review available laboratory test results including hemoglobin, hematocrit, and coagulation profiles 1
• Order additional laboratory tests depending on patient's medical condition (e.g., coagulopathy, anemia) 1
• Perform preoperative evaluation well in advance (several days to weeks) to allow for proper patient preparation 1

Common Clinical Pitfalls to Avoid

Do not order daily blood tests as routine practice. Studies show that provider education reducing daily blood test orders decreased CBC from 1.46 to 1.37 tests per patient per day and basic metabolic panels from 0.91 to 0.83 tests per patient per day, saving $6.33 per patient day. 3

Do not transfuse RBCs in hemodynamically stable, non-bleeding ICU patients with hemoglobin >7 g/dL. Transfusing at a threshold of 7 g/dL is associated with similar or improved survival, fewer complications, and reduced costs compared with higher transfusion triggers. 1

Recognize that 17.3% of ordered tests may have no perceived utility. Tests should be ordered to answer specific questions about diagnosis, prognosis, treatment, or screening, with consideration of patient age and comorbidities. 4

When Blood Tests Are Specifically Indicated

Order blood tests when:

• Clinical presentation suggests acute pathology requiring immediate diagnosis (e.g., suspected acute coronary syndrome, sepsis, severe bleeding) 1
• Results will directly change management (e.g., anticoagulation monitoring, medication dosing adjustments) 1
• Baseline assessment is needed before procedures or new treatments 1
• Risk stratification is required for chronic disease management 1
• Screening for comorbidities that impact treatment decisions (e.g., diabetes, renal dysfunction, thyroid disease) 1

Blood testing plays a vital role in prevention, diagnosis, and management of chronic diseases, but must be used judiciously to maximize benefit while minimizing harm and cost. 5