Blood Test Interpretation: A Systematic Approach
I cannot provide specific interpretation of your blood test results without seeing the actual values, test names, and reference ranges. However, I can guide you through the systematic approach to understanding any blood test results.
Essential Framework for Interpreting Blood Tests
Always interpret blood test results in the context of local laboratory-specific reference ranges, as these vary between institutions and testing methods. 1
Step 1: Verify Test Reliability
Before interpreting any result, assess for factors that may render results unreliable:
Check for hemolysis - Hemolyzed samples can produce falsely elevated or decreased values for multiple parameters. If your report indicates hemolysis, discuss with your physician whether repeat testing is needed, as some altered results may still be clinically useful with appropriate interpretation 2
Review timing and collection factors - Time of collection, hydration status, and recent medications can significantly affect results 1
Identify pre-analytical issues - Improper venipuncture technique or in vitro hemolysis can cause artifactual elevations, particularly in potassium measurements 3
Step 2: Compare Against Reference Ranges
Use the specific reference ranges printed on your laboratory report - Do not rely on general ranges from other sources, as methods vary 1
Recognize that reference ranges differ by age - Adult and pediatric ranges are not interchangeable 1
Serial measurements are more valuable than isolated results - A single abnormal value may be transient; trends over time provide better clinical information 1
Step 3: Consider Clinical Context
Abnormal blood test results should never be interpreted in isolation. 4
Single abnormal values are often non-specific and cannot definitively diagnose or rule out disease 4
Multiple abnormal results increase diagnostic probability - The likelihood of significant pathology increases with the number of abnormal tests 4
Certain physiologic states alter results without indicating disease:
Step 4: Understand Test-Specific Limitations
For specialized testing, additional considerations apply:
Antiphospholipid antibody testing requires two positive tests at least 12 weeks apart to rule out transient positivity 5
Glycemic markers (HbA1c) reflect 2-3 months of average glucose control and should only be compared using assays certified as traceable to standardized reference methods 5
Natriuretic peptides (BNP/NT-proBNP) exhibit high biological variability; changes of approximately 85% for increases and 46% for decreases are needed to be clinically significant 5
Step 5: Recognize When Expert Consultation Is Needed
If results are marked as "borderline" or "uncertain," repeat testing is typically indicated rather than clinical action 5
Automated analyzer flags or comments indicating interference require laboratory or specialist review 6
Results obtained during anticoagulation therapy require careful interpretation and may need repeat testing off medication 5
Critical Pitfalls to Avoid
Never act on a single abnormal result without clinical correlation - Most abnormalities are non-specific 4
Do not compare results across different laboratory methods or assays - Cutoffs and reference ranges are method-dependent 5
Avoid interpreting results without knowing medication history - Many drugs interfere with testing 5, 3
Do not ignore laboratory comments or flags - These indicate potential reliability issues requiring attention 6
Next Steps
Bring your complete blood test report with reference ranges to your physician for interpretation in the context of your specific clinical situation, symptoms, medical history, and current medications. 1 Your physician can determine which abnormalities require action, which need repeat testing, and which are clinically insignificant in your particular case.