Comparison Verification of New Lab Equipment's & Quantitative Test Methods in Medical Lab

Following step by step Instructions suggested for verification of new equipment or method (or Reagent) used in the medical lab prior to testing patient sample analysis. 

The instruction was provided in simplified manner for better understanding by the Medical laboratory professionals.

1. Comparison of New Equipment/Method is done with comparative equipment/Method prior to use.

2. Harmonization for Primary Equipment/Method and Backup Equipment/Method are done once in 12 months.

3. Minimum 20 different patient samples are tested by the two equipments/Methods.

4. In addition to patient samples, such as certified reference materials (Analyte Calibrator), Proficiency testing samples, Quality control materials can be included in comparison study.

5. The samples should be selected to cover the entire reportable range of the equipment/method.

6. Samples should generally be analyzed within 2 hours of each other by the test and  comparative method/Equipment.

7. A minimum of 5 days is recommended, but it may be preferable to extend the experiment for a longer period of time (Probably extend for 20 days). The comparison study can cover a similar period of time and required 2 to 8 patient samples per day.

8. Graph the results immediately on a difference plot (Bland-Altman Plot) and inspect for discrepancies.

9. Re- Analyze the samples that give discrepant results to eliminate outliers and identify.

10.After completion of study (after 5 days) prepare a comparison plot for all the data to assess the range, outliers and linearity.

11. Calculate the correlation coefficient (r). r value should be 0.95 or greater. This is mainly useful for assessing whether the range of data is wide              enough to provide good estimates of the slope (b) & intercept (a).

12. Calculate the systematic error (SE) at medical decision concentration (Xc) is then determined by calculating the corresponding Y –Value (Yc) from        the regression line, then taking the difference between Yc & Xc as follows

                                    Yc = a + bXc

                                   SE = Yc – Xc 

13. Calculate the Random Error (RE) from the standard deviation (SD) obtained from replicate experiment (Precision Verification) by using repeated            20  runs of same patient  sample (or) Quality control material 

                                  RE = 3 ´ SD

14. Derive the Calculated Total Error ( TE_calc )  by

                                 TE_calc  = SE + RE

15. Method/Equipment performance is acceptable when this calculated total error (TE_calc )   is less than the  allowable total error (TE_a).

16. Refer CLIA guidelines for proficiency limits and biological variation values for fixing the  acceptable total  allowable error (TE_a).

Example - Equipment/Test Method Comparison Report  Format (Developed in MS-Excel): 

Reference Source :         

• Basic Method Validation, 3^rd Edition, James O. Westgard,PhD
• NABL - 112 Guideline (Specific Criteria for Accreditation of Medical Laboratories)

POSTED BY: 

Mr.V.SELVAM, M.Sc (Biochemistry)

Consultant - ISO 9001 & NABL (ISO 15189 & ISO 17025)

MindEmits Consulting Services, 

Chennai, Tamilnadu, India

✆ +91-9940014466

☭  selvam.mindemits@gmail.com