The Delta check a key to valid results.pptx

Laboratory medicine

1. Delta check : a key to valid results Dr. Yousr Salem El-Sheikh Master of Clinical & Chemical Pathology Egyptian Fellowship in Clinical Pathology TQM in Healthcare Reform AUC

2. Definition A comparison of two consecutive results from the same patient, based on specified criteria as a quality improvement effort by the lab. Difference between two sets is compared to a pre-defined limit that is specific for the analyte within a pre-defined length of time.

3. Goals

4. Concept of delta checks

5. Causes of discrepant results

6. preanalytical A) Patient misidentification JC NATIONAL PATIENT SAFETY GOALS: 1. Minimum two unique identifiers for each patient. 2. Label samples Infront of the patient. Mislabeled (One or more identifiers are incorrect) Misidentified (Wrong blood in tube) NICU, ER, Geriatric patients, Language barriers, identical names

7. Preanalytical B) Specimen related issues Source of variation Effect on laboratory result I.V. fluid dilution False increase in corresponding analytes & dilution of other analytes Improper anti-coagulant EDTA: increased K Decreased Ca, Mg & Alp Order of blood tube collection Contamination of subsequent blood tubes with anti-coagulants, preservatives or other additives Long tourniquet time Concentration of analytes, false increase of K, NH3, Lactate Serum separator tubes Gel may adsorb small molecules such as drugs, not recommended for use in TDM

8. Preanalytical C) Post collection Sample transport Timing: Offsite blood drawing, delayed centrifugation, WBC glucose utilization, leakage of RBCs contents Temperature: ABG, Ammonia. Light exposure: Bilirubin, Vitamins. Centrifugation: timely separation of serum and cells. Delayed separation affects glucose, K, LDH, Ammonia Excessive spin: Hemolysis due to RBCs’ membrane damage. Storage: Labile analytes must be frozen.

9. Causes of discrepant results

10. Analytical variation Instrument specific issues Reagent problems, variation in reagent volumes, delivery Inter-instrument differences when more than one instrument are used. Calibration Errors in pipettors or probes. Air bubbles Method specific issues Dilution errors Improper mixing pH or temperature changes. Reagent, lot changes.

11. Causes of discrepant results

12. Biological variation

13. Delta check calculation modes Different calculations of delta check values are possible when quantitative data is available including: Absolute change. Percentage change. Rate of change. Various multivariate approaches Complex calculations of change involving more than one analyte over consecutive samples such as anion gap or urea creatinine ratio.

14. Approaches to determine limits for signaling delta check

15. Biological variation

16. Reference Change Value (RCV) Is the difference between serial measurements statistically significant?? It can be used to determine a delta check limit Should be used with analytes with high individuality index “Significant Change Value”

17. Reference Change Value (RCV) Z = for 2 tailed analytes 1.96 at 95% probability (Significant) 2.58 at 99% probability (Highly significant) CVA: Analytical variation (From QC results) CVI: Intra-individual variation (From literature or http://www.westgard.com/biodatabase1.htm

18. Limits derived from patient data three approaches to set limits 1. Empirical Approach (Logical approach) Keep a deltacheck log List the previous and current results that have delta check alerts. Note about the outcome of the investigation Some analytes are more useful in delta checks Little day to day variation Low RCV Low index of individuality Creatinine, ALP, Urea, Bilirubin, MCV

19. Limits derived from patient data three approaches to set limits 2. Distribution of delta values in the patient population Download patient data for the analyte into a spreadsheet Sort the data by patient name or medical record number Calculate the delta differences and time differences between consecutive results Limit the time between the results Express the differences in whatever manner

20. Limits derived from patient data three approaches to set limits 3. Simulation of misidentified specimens Intentionally mislabel specimens Analyze to see if delta check procedures give an alert when a problem specimen is analyzed Log this information Adjust the time periodically

21. Time interval between specimens General rule Correlation between results decreases as time interval increases Delta checks are recommended for inpatient testing Percentage rate of change is helpful for delta checking analytes that display large changes over time Generally select chemistry analytes that have the lowest biological variation

22. Time interval between specimens Example of delta check limits for some analytes Analyte Limit Albumin 2.0 g/dl Bilirubin 2.0 mg/dl BUN 25 mg/dl Calcium 3.0 mg/dl Chloride 15.0 mEq /L Creatinine 1.0 mg/dl Magnesium 2.0 mEq /L Potassium 2.5 mEq /L Sodium 15 mEq /L Total protein 2.0 g/dl MCV 5.0 fL MCHC 5.0 g/dl

23. Implementing delta checks in LIS Considerations for determination of delta check limits: Time interval Expected minimum change during this time interval based on: Qualitative change Absolute or percentage difference Increasing and decreasing in differences Varying rules depending on whether the result is below, within or above the reference interval Pathological states Hospital location, ordering physician, changes from reference interval

24. To report or not to report There is a fine balance between cancelling questionable results and reporting them: Implication of result cancellation: Difficult to redraw Neonate issues Loss of blood volume Delayed treatment Delayed discharge Implication of reporting incorrect results: Lengthened hospital stays, inappropriate medical care, economic, psychological and social issues Implications beyond chemistry and hematology Transfusion services Immunology Infectious diseases Genetic and molecular testing Harm may not be realized for hours, days or years

25. General Checklist: Starting the investigation Repeat analysis Confirm correct patient was analyzed Make new aliquot, if applicable Investigate pre-analytical issues Correct sample type(Serum, plasma, whole blood) Gross hemolysis, icterus, lipemia (Check for hemolysis of whole blood samples) Clots, air bubbles

26. General Checklist: Starting the investigation Investigate analytical issues QC, proper reagents, proper calculations Isolated event or others from same run All check out?? Consider biological explanations….

27. General tips to confirm discrepant results Do lab values match previous results? Look at test history and overall trends Look at more than two results to confirm trends Where the previous results questionable? Look at patient location (NICU, Oncology, ER…) Was a type and screen ordered? (Suggests transfusion) Where TDM tests ordered? (Not detected suggest possible misidentification)

28. Wrap up Delta Checks can be a useful tool for detecting Sample quality issues, sample misidentification and biologically relevant changes in patient status Pre-analytical errors, analytical errors and biological variations are possible causes of discrepant results Delta check limits should be tailored to particular patient populations Consequences to patient care must be considered when deciding to cancel or report a discrepant result

29. References CLSI. Use of Delta Checks in the Medical Laboratory. 1st ed. CLSI Guideline EP33. Wayne, PA: Clinical and Laboratory Standards Institute; 2016. https://www.westgard.com/biodatabase1.htm Ricos C, Alvarez V, Cava F, Garcia-Lario JV, Hernandez A, Jimenez CV, Minchinela J, Perich C, Simon M. "Current databases on biologic variation: pros, cons and progress." Scand J Clin Lab Invest 1999;59:491-500. Schifman R. et al. Delta Check Practices and Outcomes: A Q-Probes Study Involving 49 Health Care Facilities and 6541 Delta Check Alerts. Archives of pathology & laboratory medicine 141(6) · April 2017