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A program to calculate and chart monthly QC.

A number of control vendors produce monthly quality control charts for their laboratory customers, but the labs still have to prepare charts of their own for other analytes. I developed a software-application program called QC.EXE to simplify the task of working up a QC chart from scratch.

Written on Microsoft's Quick Basic 3.0 software for use with IBM compatible microcomputers, the program can be executed from a floppy disk or a hard disk; no additional program is needed to make it work, nor is a graphics card required. A printer capable of operating in compressed mode, such as an Epson or Epson compatible, is essential. The width of an 8 1/2 x 11 sheet of paper normally takes about 80 characters, but the 31 days on the QC graph require 137 characters across the page. QC.EXE uses a parallel interface (LPT1) for printing.

The program size is about 85,000 bytes. Text files-each accepting control values for a different analyte-are created by QC.EXE as needed. With simple menus guiding the input, users do not have to know mu computer applications.

Developing QC.EXE in the first place was a different story. I had taken several computer classes at a community college, and this was my first attempt at writing a program for the lab. It took months of my spare time to iron out the wrinkles. Thanks to the experience,

though, work on the next program I tried (a larger one for staff scheduling) went much faster.

If you use a calculator to record and manipulate quality control data, you probably must enter all of the QC values in one stretch at the end of the month, and if you make a mistake, you may have to start over because there's no way to retrieve the incorrect value. With QC.EXE, you can enter accumulations of data whenever you wish during the month; they will be saved until you delete them. If you make a mistake, you don't have to start over-just delete the incorrect value and continue.

The program hurries the QC statistical process in several ways. It calculates the standard deviation, mean, and coefficient of variation. It also tells you the

number of QC values in a file, the sum of the values, and the median if you ask that the values be sorted in ascending order. (The file is not permanently sorted, however. When you go back to the file list menu, the values revert to the order in which they were entered.) And, as we have noted, the program creates a graph if the you want one.

Let's take it step by step. First type the command to run the program. At the DOS prompt, type in "QC" and press return. That will bring on the first screen, my disclaimer of responsibility for problems that may arise from use of the program. This is followed by a screen describing in general what the program does.

Pressing any key gets you to the main menu. The user programs this menu, with file names of different analytes for which quality control will be per-

formed. That's done by selecting menu item 22, "Reprogram file list menu," and following the instructions on the screen that appears.

There are two input boxes on the screen. One is for the file number, the other for the new file name of up to I I characters to go with the file number. When you have entered the file name, type Quit"

and the main menu will reappear.

You can enter data in a file by selecting the file number. This brings you to another menu with six options.

Option I displays the file contents, if any. Option 2 deletes all QC values in the file so you can start entering new values. Option 3 is used for adding values. If a patently incorrect entry is made,

such as a combination of numbers and letters instead of just numbers, the computer will beep and flash an error message ("Not a real number, please reenter"). Option 4 lets you delete one or more QC values. Option 5 is for returning to the file list menu. And option 6 leads to a menu for sorting values, or displaying file contents and calculations or creating a kind of QC graph.

To print a graph, you must decide how many standard deviations you want to measure. You also must enter a number that will divide the standard deviations into increments of QC values. These increments form the index on the vertical side of the chart. Finally, you are asked to indicate the number of decimal places for the calculations, from 0 to 3.

If the entries are acceptable, the chart can go to the printer. One problem that the program alerts you to, by displaying a message at the bottom of the screen, is an excessive number of increments. This leads to insufficient spacing between values in the chart index and repetition of some values, since they are calculated (standard deviations divided by the number of increments) and rounded off. The message will suggest fewer increments to increase the space between values.

From time to time a value is skipped on the index, again because the values are calculated and rounded off. This can't be helped.

Some control vendors will cal-

culate your standard deviation, mean, and coefficient of variation but will not provide a graph. In such instances, the program can print blank graphs for manual plotting.

Entry of the following calculated numbers-where X is the known mean, and S is the known standard deviation-will generate such a graph:

First number = X + [Square-Root of](.5(S[.sup.2])) Second number = X -[Square-Root of](.5(S[.sup.2]))

Readers who are interested in obtaining a floppy disk containing this quality control program can write to the author at P.O. Box 20644, Portland, Ore. 97220. Include your address and a check for $2.50, which will cover the cost of a 5/4-inch floppy disk (do not send a disk to the author), a suitable mailing package, and postage. The software is free.
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:quality control computer program
Author:Moore, Michael E.
Publication:Medical Laboratory Observer
Date:Jul 1, 1989
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