SMILE

JohnsHopkinsUniversity

Baltimore, MDUSA

Carryover Guidelines

Name of Procedure
Serum Carryover Procedure / Guideline Number / Equ35-I-01-G
Effective Date / 6 October 2009
Subject
Serum Carryover Guidelines / Page / 1 of 4
Supersedes / New
SMILE Comments: This document is provided as an example only. It must be revised to accurately reflect your lab’s specific processes and/or specific protocol requirements. Users are directed to countercheck facts when considering their use in other applications. If you have any questions contact SMILE.
Carryover Guidelines / Document Number / 050
Effective Date / 21 Sep 09
Subject
Guidelines for performing carryover studies / Page / 1 of 1
Supercedes / New
Author(s) / Name, Title / Date
Jo Shim MBA, MT(ASCP) / Sep 09
Approved by / Name, Title / Date
Penny S. Stevens, MBS, MT (ASCP), CLS (NCA) / 21 Sep 09
Review History / Date of last review: / 11 Aug 2010
Reviewed by: / Heidi Hanes
Revision History / Version # [0.0] / Revision Date [dd/mm/yy] / Description (notes)

SMILE Carryover Guidelines

Purpose:

“Carryover” in laboratory testing, is defined as “the contamination of a specimen by the previous one”.3. Carryover testing is performed to help to prove or disprove carryover from the sample probe in clinical laboratory testing.

This procedure outlines the steps for testing instruments for carryover from very high specimens being analyzed as part of a run. Two specimens, one very high and one very low are selected and analyzed in a specific order. Statistical analysis is performed using a spreadsheet (See Appendix 1) to determine if there is a statistical difference when a very low specimen is analyzed following a very high specimen.

Definitions:

Low-Low Results – A low result that immediately follows another low result

High-Low results – A low result that immediately follows a high result.

Precautions:

Use Standard precautions and appropriate Personal Protective Equipment as outlined in the lab Safety manual.

Procedure:

Step / Action
1 / Select specimens for the analytes to be tested. Select one patient specimen with a very low level of the analyte and one with a very high level. Select specimens with enough volume so that they can each be run approximately 10 to 11 times.
If / Then
Patient specimens are not available. / Select appropriate controls or EQA specimens.
2 / Perform start-up testing as identified in the instrument operations SOP and run QC following the established procedure.
3 / Do not run any other specimens while carry over testing is being conducted
3 / Run the samples on the same run in the following order:
3 Low specimens
2 High specimens
1Low specimen
2 High specimens
4 Low specimens
2 High specimens
1 Low Specimen
2 High specimens
1 Low Specimen
2 High specimens
1 Low Specimen
If / Then
The specimens are not analyzed on the same run in the correct order / The results are invalid.
4 / Record your results and enter them into the spreadsheet (see Appendix 1) or into EP evaluator or a similar data analysis program.

Results:

The spreadsheet (Appendix 1) will calculate the SD of the Low-Low results. The error limit is equal to three times the Low –Low SD. The Carryover test passes if the carryover is less than the error limit

References:

  1. College of American Pathologists (CAP):Serum Carryover Survey Product information, downloaded from 17 August 2009
  2. EP Evaluator 8.0.0. Carryover – Report Interpretation Guidelines, David G. Rhodes and Associates Inc.
  3. Kaplan L. A., Pesce A. J., Clinical Chemistry –theory, analysis and correlation: The C. V. Mosby Company St. Louis 1984

Appendices:

  1. Appendix 1 - Carryover Spreadsheet.

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