Letters To The Editor
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Virol. May 12, 2016; 5(2): 85-86
Published online May 12, 2016. doi: 10.5501/wjv.v5.i2.85
Determination of 50% endpoint titer using a simple formula
Muthannan Andavar Ramakrishnan
Muthannan Andavar Ramakrishnan, Division of Virology, Indian Veterinary Research Institute, Uttarakhand 263138, India
Author contributions: Ramakrishnan MA designed, validated the assay and wrote the letter.
Conflict-of-interest statement: None.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Muthannan Andavar Ramakrishnan, Senior Scientist, Division of Virology, Indian Veterinary Research Institute, Mukteswar Campus, Uttarakhand 263138, India. maramakrishnan@gmail.com
Telephone: +91-5942-286346 Fax: +91-5942-286347
Received: January 7, 2016
Peer-review started: January 10, 2016
First decision: March 1, 2016
Revised: March 2, 2016
Accepted: March 17, 2016
Article in press: March 19, 2016
Published online: May 12, 2016

Two commonly used methods for calculating 50% endpoint using serial dilutions are Spearman-Karber method and Reed and Muench method. To understand/apply the above formulas, moderate statistical/mathematical skills are necessary. In this paper, a simple formula/method for calculating 50% endpoints has been proposed. The formula yields essentially similar results as those of the Spearman-Karber method. The formula has been rigorously evaluated with several samples.

Keywords: Endpoint dilution, TCID50, Spearman-Karber, Reed and Muench

Core tip: The formula described in this manuscript can be used to calculate 50% endpoint titre such as TCID50%, LD50, TD50, etc., in addition to the currently existing methods. The proposed formula can be applied without the help of calculator or computer.