What are the causes of delta checks in laboratory results?

Causes of Delta Checks in Laboratory Results

Delta checks can be triggered by any of the above options (specimen or patient misidentification, transfusion or recovery from anemia, IV dilution, analytical error), as they all represent potential causes for unexpected changes in sequential laboratory values. 1

What Are Delta Checks?

Delta checks are post-analytical verification tools that compare the difference between sequential laboratory results from the same patient against predefined limits. When a difference exceeds these limits, the delta check is triggered, indicating a potential error that requires investigation 2.

Primary Causes of Delta Checks

1. Specimen or Patient Misidentification

• Wrong blood in tube (WBIT) errors occur when specimens from one patient are mislabeled with another patient's identifiers 3
• These errors represent a significant patient safety concern and were historically the primary reason delta checks were implemented 4
• Studies show that multivariate delta check approaches are more effective at detecting misidentification errors than single-analyte approaches 5

2. Transfusion or Recovery from Anemia

• Rapid changes in hematological parameters following transfusion can trigger delta checks 3
• Recovery from anemia can cause significant changes in red blood cell counts and hemoglobin levels
• These physiological changes may be clinically appropriate but still trigger delta checks

3. IV Dilution

• Intravenous fluid administration can dilute blood samples, particularly if drawn from the same limb as the IV
• This causes artificial decreases in multiple analyte concentrations
• Particularly common with electrolytes, proteins, and cell counts

4. Analytical Error

• Instrument malfunction, calibration issues, or reagent problems can cause unexpected changes in results
• Delta checks can identify these analytical problems before erroneous results are reported 4
• In cardiac marker testing, analytical errors can be detected through delta checks when values don't follow expected patterns 1

Clinical Applications of Delta Checks

Delta checks have evolved beyond simple error detection and are now used in specific clinical scenarios:

1. Acute Kidney Injury Detection: Using changes in serum creatinine 6
2. Cardiac Marker Evaluation: Delta measurements of cardiac troponin and CK-MB help detect acute myocardial infarction with high sensitivity and specificity 1
3. Monitoring Rapid Electrolyte Changes: Particularly for serum sodium to prevent osmotic demyelination syndrome 6

Implementation Considerations

When implementing delta checks, laboratories should:

• Select analytes with low indices of individuality for better performance 6
• Balance sensitivity and specificity to minimize false alerts while catching true errors
• Consider using machine learning-based multianalyte approaches for better detection of WBIT errors 5
• Establish appropriate delta thresholds based on evidence rather than opinion 2

Common Pitfalls

• Excessive delta check alerts can lead to alert fatigue and reduced effectiveness 1
• Simple univariate delta checks often have poor specificity, leading to many false positives 3
• Delta check investigations are time-consuming and resource-intensive 6
• Failure to distinguish between physiological changes and true errors can delay result reporting

Delta checks remain a valuable quality tool in laboratory medicine, but their implementation requires careful consideration of analyte selection, threshold setting, and verification to balance error detection with operational efficiency.