Are Routine Blood Tests Automatically Performed on Every Emergency Department Patient?
No, routine blood tests are not automatically performed on every emergency department patient—testing should be selective and guided by the patient's clinical presentation, history, and physical examination findings. 1
Evidence-Based Approach to Laboratory Testing in the ED
The Selective Testing Standard
The American College of Emergency Physicians provides Level B recommendations stating that in adult ED patients with primary psychiatric complaints, diagnostic evaluation should be directed by history and physical examination, and routine laboratory testing of all patients is of very low yield and need not be performed as part of the ED assessment. 1
History and physical examination predict 83-98% of clinically significant abnormalities in psychiatric patients, making clinical assessment far more valuable than reflexive testing. 2
Why Routine Testing Is Not Standard Practice
- Extensive routine laboratory panels have extremely low yield (0.8-1.4%) when history and physical examination are normal. 2
- False positive laboratory results are 8 times more common than true positives (1.8%) in patients undergoing routine testing. 1, 2
- Only 4% of ED patients with psychiatric complaints required acute medical treatment within 24 hours, and in 83% of cases, history and physical examination were sufficient to identify those who needed intervention. 1
When Testing Should Be Performed
Testing should be targeted based on specific clinical indicators rather than performed reflexively: 2, 3
- Check serum glucose if hypoglycemia or hyperglycemia is suspected based on history or examination findings. 2, 3
- Order electrolytes when medication use, excessive water intake, or clinical presentation suggests metabolic disturbance. 2, 3
- Obtain CBC when infection is suspected based on fever or immunocompromised status. 2, 3
- Use a lower threshold for testing in elderly patients, those with substance abuse history, patients without prior psychiatric history, and those with abnormal vital signs. 2, 3
High-Risk Populations Requiring More Comprehensive Evaluation
Certain patient presentations mandate broader testing regardless of initial impression: 4, 3
- Patients with altered mental status, disorientation, or confusion indicating possible delirium. 4, 3
- Those with abnormal vital signs including fever, tachycardia, hypertension, or hypotension. 4, 3
- Elderly patients without prior psychiatric history. 3
- Patients with focal neurological deficits or signs of cerebrovascular disease. 4
Common Pitfalls to Avoid
Do not order extensive routine laboratory panels reflexively without clinical indication. 2, 3 The evidence consistently demonstrates that clinical assessment should drive testing decisions, not institutional protocols or defensive medicine practices.
Do not assume psychiatric etiology without excluding medical causes in high-risk groups such as the elderly, first presentations, patients with abnormal vital signs, or those with substance abuse history. 3
Do not delay psychiatric evaluation waiting for laboratory results in alert, cooperative patients with normal vital signs and noncontributory history and physical examination. 2
The Reality of Current Practice
While guidelines recommend selective testing, research shows significant variation in practice patterns. One study found that 62.2% of blood tests performed in an ED were inappropriate based on clinical guidelines, with only 3.8% influencing diagnosis and 3.0% influencing patient care. 5 This highlights the gap between evidence-based recommendations and actual clinical practice, often driven by institutional culture rather than patient need.