First Step in Managing Abnormal Lab Values
The first step is to verify the abnormality is real by checking for laboratory error, physiologic variation, and comparing to previous baseline values, while simultaneously conducting a focused history and physical examination to identify clinical correlates that would explain the abnormality. 1, 2
Immediate Verification Steps
- Review all previous lab results before ordering additional investigations to establish whether this represents a true change from baseline or chronic abnormality 1
- Check for plausibility of the result by considering whether it fits the clinical presentation, as laboratory variation and physiologic variation are the most common causes of abnormal results 3, 4
- Repeat the test if the abnormality is unexpected and doesn't correlate with clinical findings, as false positives occur 8 times more frequently than true positives in routine screening 5
Concurrent Clinical Assessment
- Obtain a targeted history focusing on symptoms that correlate with the specific lab abnormality, as history and physical examination predict the majority of patients who will have clinically significant laboratory abnormalities 5
- Perform a focused physical examination looking for signs that would explain the abnormality (e.g., fever, altered mental status, focal neurologic deficits, jaundice, signs of liver disease) 5
- Review all medications, supplements, and substances including over-the-counter drugs, as drug-induced abnormalities are common and often reversible 5, 2
Pattern Recognition and Severity Assessment
For elevated liver enzymes specifically:
- Measure both aminotransferases (ALT, AST) and cholestatic markers (ALP, GGT, bilirubin, albumin, PT/INR) to determine the pattern of injury 1, 2
- Check serum creatine kinase (CK) to exclude muscle injury as the cause of elevated AST 1, 2
- Classify severity: mild (<5× ULN), moderate (5-10× ULN), severe (>10× ULN), or life-threatening (>20× ULN) 2
Critical Decision Points
Stop all potentially hepatotoxic medications immediately if:
- ALT/AST exceeds 5× ULN, OR
- Any elevation occurs with jaundice or elevated bilirubin, regardless of absolute enzyme level 6, 1
The history and physical examination will identify the cause in the vast majority of cases - laboratory testing should confirm clinical suspicions rather than drive the diagnostic process 5, 7
Common Pitfall to Avoid
Do not anchor on referral data or previous diagnoses - treat the patient as if presenting for the first time and conduct your own assessment, as cognitive biases from referral information frequently lead to diagnostic errors 8. The most frequent error is ordering extensive laboratory testing without clinical indication, which yields abnormalities that are clinically insignificant in 80-90% of cases 5, 4.