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Impress your inspectors with linearity graphs.

Impress your inspectors with linearity graphs

Instrument operation manuals and reagent package inserts routinely list acceptable ranges for accurate results of the tests done on or with them. Yet the organizations that inspect and accredit or license hospital laboratories don't want laboratorians to follow these guidelines from manufacturers. Instead, CAP, JCAHO, and our state Department of Health and Rehabilitative Services all require that labs regularly demonstrate linearity for each procedure; individual inspectors are the ones who decide how often "regularly" is. In our case, we have to do it at least twice a year.

Our state inspectors have the authority to fine us, stop us from doing certain tests, and even close us down. Sharp-looking computerized reports tend to make the inspectors happy, and when they're happy, we're happy.

* Easing the way. Proving linearity for a large number of procedures can be extremely time consuming. Preparing graphs for each procedure by hand is highly labor intensive. Furthermore, it tends to produce smeared, messy results that the inspectors frequently scrutinize more closely than professional-looking computer printouts. A spreadsheet makes the task a snap.

I have prepared linearity graphs for several years with Lotus 1-2-3, Release 2 (Lotus Development Corp., Cambridge, Mass.), operating on an IBM PC/XT or a PS2/Model 30 personal computer. The software will operate on most IBM-compatible equipment. If you don't own Lotus 1-2-3, a number of other spreadsheet programs, including Excel (Microsoft) and Quattro (Borland International) have similar capabilities with slightly different commands. A printer with a graphics display module completes the necessary equipment. Color printers are easier to use and create prettier results, but my monochromatic one does just fine.

I have found it is more efficient to accumulate data every few weeks and produce all the linearity graphs in a single session. To speed the operation, I created a macro that I keep in an otherwise blank worksheet, which I use as a template. That way it's always available and I don't have to keep recreating it.

* Creating the macro. Load Lotus in the normal manner for your setup. I use the first dozen or so lines of my macro file for reminders on how to proceed (Figure I). Use the down arrow ([down arrow]) to go to line 18, where the macro begins.

When using this macro, precede with an apostrophe (') any entry beginning with a forward slash (/) or a backslash (\). Taking this step will prevent the program from recognizing the subsequent characters as commands. The apostrophe will not be visible on the screen, even as a space, although it will appear on the status line at the top of the screen as you work.

The name of the macro (\g) is in cell A18. Commands are in cells B18 through B29. The explanations in column D serve as reminders only and may be omitted if you have a wonderful memory.

The forward slash (/) calls the menu. Other commands are called by the first letter of the command.

Enter the information as shown in the lower section of Figure I, remembering to use the apostrophe where needed. When you're done, return the cursor to "\g." Type this sequence, representing Menu, Range, Name, Label, Right:

/RNLR You will have assigned the name "\g" to the macro in column B.

Save your worksheet by typing the following sequence, which represents Menu, File, Save, and the file name (since file names are limited to eight characters, spelling must occasionally, as here, be sacrificed):

/FSLINEARTY Now press <ENTER>. Whenever you need to produce linearity graphs, you'll be able to retrieve this file.

Do you have all your data ready? You will need the assay values, the results recovered, and the lot numbers of the reagents or linearity material used. Load Lotus and retrieve the linearity file by typing the following sequence:

/FRLINEARTY and pressing <ENTER>. The keystrokes stand for Menu, File, Retrieve, and the file name.

* Entering data. Type in your data. Be sure to precede all lines indicating lot numbers and dates by an apostrophe. This acts as a flag, alerting the program that what follows is text, not a formula. Otherwise, the program will read the slashes as commands for division and calculate the date as a number. The date 10/22/89, for example, would be entered:

'10/22/89 Without the apostrophe to deflect it, Lotus would divide 10 by 22 and the result by 89, obtaining 0.0051072--not exactly what you had in mind.

Each set of data occupies only a small amount of space. To keep everything on a single screen (and then on one page of printout), I space the sets in three columns across the screen rather than running them vertically (Figure II).

* Graphing. It's most convenient to create each graph immediately after entering the appropriate data. Call the macro. Holding down <ALT>, press "g" (for "go"). A request for ranges will appear on the screen. Use the "X" range for assay data and the "A" range for recovered data. Move the cursor to the first value in the proper column, press the period key (.), and move the cursor to the last value in the column. All values will be highlighted.

Press <ENTER>. The macro will advance to the next section that requires a keyboard entry.

As with file names, the title of each graph can consist of no more than eight characters. When creating the name, incorporate the date so that you can store a full year's graphs on a single disk. An example: GLUJAN90 (for glucose graphed in January 1990).

After you have made all necessary responses, the graph will be displayed. Save it for printing later. Press any key to return to the worksheet. Then enter the next set of data.

* Saving and printing. To save a file after completing the worksheet, when the prompt comes up to save the file, enter a different name from the one you started with, such as LINOCT89. This will protect your template, which would otherwise be erased when you stored your current work. Then print the worksheet. Since our state and CAP inspectors require that the data and graph appear on a single page, I cut each data section from the printout and tape it to the appropriate graph.

You may have one of the fancy programs, such as Allways (Funk Software, Inc., Cambridge, Mass.), that combine text and graphics on a laser printer. These programs are impressive but very slow. I have no such program available and couldn't monopolize our printer that long anyway.

To print the graphs you want from Lotus, you must use its program module, PrintGraph. Exit Lotus by typing the sequence:


Load PrintGraph according to the instructions in the manual. If you are operating from floppy disks, take care to use the right one. I have the programs stored in my hard disk.

Place the cursor on "Image-Select" and press <ENTER>. A list of all the graphs on your disk will appear (Figure III). Move the cursor with the up and down arrows to highlight each graph you would like to print--there's no limit to the number you may choose--and press the space bar to mark it. When you are done, press <ENTER>.

To be sure your printer is ready, arrange the paper and press "a" (for "align"), which tells the program that printing will begin at the top of the page, then "g." While my high-resolution IBM printer does a great job, it takes 15 minutes per graph. A low-resolution IBM, Okidata, or similar machine will print much faster--about four minutes per graph. On the other hand, it will produce less legible text.

As Figure II demonstrates, the finished graphs look professional and slick. You'll wow them at your next inspection! [Figure I to III Omitted]

Howard Ulstein is technical coordinator at AMI North Ridge Medical Center, Fort Lauderdale, Fla.
COPYRIGHT 1990 Nelson Publishing
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Author:Ulstein, Howard
Publication:Medical Laboratory Observer
Date:Mar 1, 1990
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