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Lotus 1-2-3 worksheet for fibrinogen calibration curves.

The method used most often to measure fibrinogen involves reacting diluted plasma with a thrombin reagent, determining how long it takes for a clot to form, and reading the fibrinogen concentration from a graph. One problem with this method is the difficulty of reading the result from the log/log graph paper that is required to plot the calibration curve.

I have designed a worksheet on Lotus 1-2-3 (Lotus Development Corp., Cambridge, Mass.) that automates the entire calibration procedure. Recently NCCLS published a recommendation(1) that a minimum of five points be used for fibrinogen calibration. This spreadsheet uses the Medical Laboratory Automation, Inc. (MLA) procedure for five levels of standards.(2)

Start by loading Lotus 1-2-3 or a compatible spreadsheet. I have tested this worksheet in Lotus 1-2-3 versions 2.01, 2.2, and 2,3 and in Quattro Pro 4.0 (Borland International, Inc., Scotts Valley, Calif.) running in Lotus mode.

* Worksheet. The first step in setting up the worksheet is to enter labels in cells D4, D5, A7, D7, A8, A9, AIO, All, and A12 (Figure 1). To make the labels appear correctly, we must change the width of the "A" column. To do this, type/WCS [ENTER], the number 12, and [ENTER]. Enter the concentration of the fibrinogen standard in cell B7; then enter the times of the five dilutions in cells B8 through B12.

In cell C8, enter the formula +B7*2. This gives the concentration of a 1:5 dilution of the standard. In cell C9, enter the formula +B7 for the 1:10 dilution. In cell CIO, enter +B7*0.67 for the 1:15 dilution; in cell CII, enter +B7*0.5 for the 1:20 dilution; and in cell C12, enter + B7'0.4 for the 1:25 dilution.

Since these numbers will look clumsy, reformat these cells to display whole numbers. Do this from cell C12 by typing/RFF [ENTER] the number 0 [ENTER], and then [.] (a period). Use the up arrow to

Move over to cell D8 and enter the function (a LN(B8). Copy this formula to cells D9, DIO, DII, D12, E8, E9, EIO, Eli, and E12. To do this, remain in D8 and press / C [ENTER]. Highlight the cells from D8 to E12 using the arrow key as above. Press [ENTER] again. Next, format these same cells so that they print only to one decimal place by typing/RFF [ENTER] and 1 [ENTER]. Highlight them and press [ENTER] again.

* Regression line. The next step is to calculate a regression line from the logs of concentration and time data. Use the arrow key to return to cell D8. Type/DR and press [ENTER] to select the X range. Highlight cells D8 to D12 and press [ENTER] to select this range. Now move to the Y range and press [ENTER]. Select E8 to E12. Move to Output Range. Type C14 and press [ENTER]; this places the regression calculation results in the cells directly beneath the data entry cells. Press G to calculate the regression data and automatically return to the spreadsheet main menu.

A handy addition to the worksheet is an insertion of the date on which the set of data was entered. Move to cell G4 and enter the function (aINT(aNOW). An unintelligible five-digit number appears. To translate it to standard date format, type/RFD [ENTER] and the number 4 [ENTER].

With the graphing routines of Lotus 1-2-3, you can display a graph of the calibration curve. To call up the graph menu, type/G. Select a line graph from the options offered. Next, select the X range on the graph, as follows: Type X, highlight cells D8 to D12, and press [ENTER]. To select the Y range, type A and select cells E8 to E12. Now select Options from the graph menu and Titles from the options menu. Select First; press [ENTER]. Type: Fibrinogen Curve; press [ENTER]. Select X axis; press [ENTER]. Type: Log of Time; press [ENTER]. Select Y axis; press [ENTER]. Type: Log of Fibrinogen; press [ENTER]. Exit this routine by typing the letter Q and pressing [ENTER]. Select View to look at the graph. Press any key to continue.

* Lookup table. The next step in setting up this spreadsheet is to make a lookup table(3). In cells A24, C24, and E24 enter the label Sec. In cells B24, D24, and F24 enter the label Fibrinogen. Enter the formula +B8 into cell A26. This copies the shortest usable time of the 1:5 dilution into the starting point for the table. In cell A27 enter the formula +A26+0.1. Now copy this formula to cells A28 through A45.

In cell C26 enter the formula +A45. In cell C27, enter the formula +-C26+0.1; then copy it to cells C28-C45. Repeat this process for cells E26-E45. Enter the formula for calculating fibrinogen (found in the cell list) in cell B26. Copy this formula to cells B27-B45.

Since the calibration curve is valid only through the time of the fifth dilution, a modified formula is used for the other columns of numbers. Enter the formula from cell D26 and copy it to cells D26 through D45. Copy the same formula to cells F25 to F43. The C. if function in this formula identifies the time in the cell next to the formula and compares it to the time of the third dilution. If the time shown is less, the program calculates a result; if it is greater, it prints NA (for "not applicable"). Finally, insert the following comment in cell A47: Note: Do not use times greater than the largest dilution ! The last task in setting up the worksheet is to specify a print range. Type/and enter the range A1..E47. At this point the fibrinogen calculator is ready to use in constructing mine, I added a menu that allows automatic data entry, graph viewing, and saving. The macro needed for this and the menu itself are listed in cells A90 through BI02. An earlier Computer Dialog article on macro menus may be of assistance here.(4)

You can go a step further with this spreadsheet by creating a stand-alone program that will not require a copy of 1-2-3 to run--and can't be accidentally modified by users. The handy tool: a spreadsheet compiler such as Baler (Baler Software Corp., Rolling Meadows, 111.).

1 National Committee for Clinical Laboratory Standards Procedure 1or the determination of fibrinogen in plasma; tentative guideline H30-T. Villanova. Pa, NCCLS, July 1991

2 Addendum to the E700 Operator's Manual Pleasantville. NY., Medical Laboratory Automation, Inc., 1983

3 Cody, BE. Lookup tables to speed data entry and reduce errors (Computer Dialog). MLO 23(6): 72 74, June 1991.

4 Scheele. K How macro menus enhance Lotus 1-2-3 (Computer Dialog)MLO 22(1): 65 67. January 1990

The author is LIS coordinator at Holy Family Memorial Medical Center. Manilowoc, Wis He wishes to thank Linda A Charles, Ph D., technical director of the clinical coagulation laboratory, Duke University Medical Center, Durham, N.C, for providing help, and Carol Amendola-Hannes of Baxter Diagnostics, Dade Division, Milwaukee area. for providing the fibrinogen calibration procedures used as examples in this article.
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Title Annotation:Computer Dialog
Author:Sehloff, James A.
Publication:Medical Laboratory Observer
Article Type:Column
Date:Jul 1, 1992
Words:1197
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