

CORRESPONDENCE 

Year : 2015  Volume
: 6
 Issue : 2  Page : 116117 


VACCRaksha Calc: A computer program for the calculation of vaccine potency
SaiMahesh Reddy Avula^{1}, Venkata Subba Reddy Avula^{2}
^{1} Department of Veterinary Pharmacology and Toxicology, Veterinary College, Hyderabad, India ^{2} Department of Pharmacology, Andhra Medical College, Vizag, Andhra Pradesh, India
Date of Web Publication  20Apr2015 
Correspondence Address: SaiMahesh Reddy Avula Department of Veterinary Pharmacology and Toxicology, Veterinary College, Hyderabad India
Source of Support: None, Conflict of Interest: None  Check 
DOI: 10.4103/0976500X.155495
How to cite this article: Avula SR, Avula VR. VACCRaksha Calc: A computer program for the calculation of vaccine potency. J Pharmacol Pharmacother 2015;6:1167 
Assessment of vaccine potency is often carried out by veterinarians in animal house in biological units. The more reliable method used for this assessment is Spearman and Karber. The calculations involved in the assessment are complex, confusing, time consuming and not easily reproducible. Spreadsheet is a computer application in which data are arranged in rows and columns of a grid and can be manipulated and used in calculations. In today's era of smart phones, tablet PCs and netbooks, where a spreadsheet program in the form of Microsoft Excel is readily accessible by most veterinarians, it should be possible to adapt the various laborious steps involved in the said method to a spreadsheet program by writing simple logical codes in the spreadsheets to do the calculations in a simple, clear, faster, reproducible, accurate and userfriendly manner. This article describes a spreadsheet program (VACCRaksha Calc) to calculate the vaccine potency based on the steps involved in Spearman and Karber [Figure 1].  Figure 1: Calculation sheet used in the laboratory (conventional method)
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Vaccine potency calculation
The spreadsheet program is based on the various steps for evaluation of vaccine potency by Spearman ^{[1]} and Karber ^{[2]} method.
According to them log _{10} of end point dilution of vaccine is given by the formula
 [X_{o}  D/2 + D (∑ R/N)]
Where:
X_{o} = log _{10} of the reciprocal of the lower dilution at which all animals are protected
D = log _{10} of the dilution factor
R = number of mice died due to specific symptoms
N = number of animals used at each individual dilution (after discounting accidental or nonspecific deaths)
The spreadsheet program used is Microsoft Excel version 2013. ^{[3]}
Coding and logical data used in this program are as follows;
For D11 cell (mice alive)
=D9D10 (also applied for E, F and G11 cells)
For D13 cell (sum of r/n) it's been,
=IF (E12 < 1, D12 + E12 + F12 + G12)
For E13 cell,
=IF (E12 = 1, E12 + F12 + G12)
For D14 cell (multiplication with log of dilution factor)
=0.7*D13
For D15 cell (deletion of 0.35)
=IF (E12 < 1, D140.35)
For E15 cell (addition of 0.35)
=IF (E12 = 1, E14 + 0.35)
For Antilog calculation i.e. E15 cell,
=IF (E12 < 1, 10^D15)
For D17 cell (relative potency)
=IF (E12 < 1, D16/18)
One representative study is presented to help and understand the usefulness of the program. The findings of the experiment along with the calculation are presented as a screenshot of the program [Figure 2].  Figure 2: Snapshot taken from the actual spreadsheet of potency calculation
Click here to view 
The difficulty which usually concerns veterinarians in biological units is the virus titer or end point dilution assessment. They often encounter the following problems:
 The calculations involved in the assessment are time consuming
 The calculations appear confusing when reviewed at a later date
 It is often difficult to explain in a report or communication how the final figure was arrived at.
The program described here can easily solve the above problems. It can be used to store, process, analyze and graphically represent data. A formula entered in a cell in the spreadsheet defines how the content of that cell is to be calculated from the contents of any other cell(s) each time the content of the other cell(s) is updated.
The program was thoroughly tested for the entire range of possible values. As the spreadsheet makes the whole process of assessment faster and user friendly, the program will be useful to veterinary professionals who are working in biological units.
References   
1.  Spearman C. The method of "Right and Wrong Cases" ("Constant Stimuli") without Gauss's formulae. Br J Psychol 1908;2:22742. 
2.  Karber G. 50% endpoint calculation. Arch Exp Pathol Pharmak 1931;162:4803. 
3.  Available from: http://www.office.microsoft.com/en.us/excel. [Last accessed on 2014 Dec 26]. 
[Figure 1], [Figure 2]
