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Creating a calibration data base.

Creating a calibration data base Four analyzers in our chemistry section perform 50 discrete tests that must be calibrated at intervals of 4 to 12 weeks or whenever we receive a new lot number of reagents. We have two dry-slide analyzers, a discrete pack analyzer, and a multi-task wet chemistry TDM/toxicology analyzer.

The problem is how to monitor continuously changing reagent lot numbers. Failure to record changes can bias quality control statistics, especially if uncalibrated reagents are inadvertently used to perform patient analyses.

Our solution: Create a calibration data base. Technologists, who have to be certain they are working with calibrated reagents, can review a list of current lot numbers printed out within seconds. The printout also notes recalibration dates. In the same way, a supervisor can make certain calibrated reagents are being used.

The program enables the clinical chemist to keep track of calibration frequency. We want to hold the frequency down wherever possible because calibration solutions and slides are expensive. One way to economize is to batch calibrations, and we manage our inventory so that one-third of our test reagents will be received with new lot numbers every month.

A review of all aspects of calibration monitoring led us to develop a user-friendly sequential file program. Originally designed for the IBM, PC, the program was later rewritten from the Apple IIe. It runs nearly 200 lines in BASIC.

The program is controlled through two master menus. The first lists the various test files to allow user selection of one to work on; it also provides a printout of current calibration data for all of the tests or a single test. The second menu offers laboratory personnel the options of creating reading, adding to, or modifying a particular test file.

Figure I shows the portion of the program that provides the screen display for the menu of dry-slide test files (lines 120-155). Analytes can be added or deleted as instruments are reconfigured for different tests. When the user enters a test number at line 155, logic control in line 160 permits access to the chosen analyte file among the file names listed (lines 161-183). These lines can also be readily changed.

Use of the "cal print out" option in the menu produces a listing of the most current calibration data for each test or, as in Figure II, for all of the tests on an analyzer. The data originate from a calibration printout sheet kept on the door of the refrigerator where reagents are stored. On this sheet, technologists log every calibration they perform. I then enter the information into the computer.

We don't have to figure out the prospective recalibration dates that appear on printouts. The program calculates the dates for the TDM/toxicology analyzer on a 60-day cycle and for the other analyzers on a 90-day cycle. These are optimal time spans. As I noted earlier, actual calibration intervals may be as short as four weeks.

For each test, we record particular instrument calibration parameters. The types of parameters vary from instrument to instrument. They include starting points, scale factors, slopes, intercepts, curvatures, and standard deviation of the regression line. A column for miscellaneous information also may cover a parameter--curvature data, for example, are recorded under the miscellaneous heading in the glucose calibration file for a dry-slide analyzer (Figure III).

All of the previous calibrations for a particular analyte can be recalled with a "print tabular record file" command. This list can be reviewed for potentially erroneous calibrations--those whose parameters differ markedly from the majority of previous calibrations.

In use since last October at our 500-bed medical center, the program has helped us rapidly identify uncalibrated reagent slides, packs, or kits. Another plus, from a laboratory inspection standpoint, is the easy retrieval of the program's comprehensive output.

We have also detected unusual trends--most notably, duplicate calibrations of the same reagent lot by different technologists. Guarding against such waste contributes to more cost-effective operation of our chemistry section.

Readers who wish more information about this program may write to the author at Mt. Sinai Medical Center, 1 Mt. Sinai Drive, Cleveland, Ohio 44106.
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Title Annotation:medical laboratories
Author:Sealfon, Michael S.
Publication:Medical Laboratory Observer
Date:May 1, 1986
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