ReedMuench

Reed-Muench method

The Reed–Muench method is a statistical procedure used in virology and microbiology to estimate the 50% endpoint (such as ID50, LD50, or TD50) from end-point titration data. It was introduced by Reed and Muench in 1938 as a simple way to infer the dilution at which half of the units would show an effect.

Procedure and calculation

In a typical end-point titration, a sample is serially diluted and tested for a response (for example, infection) in multiple wells or units. For each dilution, the percent of positive responses is recorded. The percent positives are then converted into a cumulative percentage, usually by summing from the highest concentration toward the lowest until the 50% threshold is crossed. Identify the two consecutive dilutions between which the cumulative percentage crosses 50%. The 50% endpoint is estimated by linear interpolation on a log10 scale of the dilutions. A common form of the calculation uses the dilutions that bracket 50% and their corresponding cumulative percentages: ED50 = log10(dilution lower) + [50 − C_lower] / [C_upper − C_lower] × log10(dilution upper / dilution lower), where C_lower and C_upper are the cumulative percentages at the lower and upper dilutions, respectively.

Applications and limitations

The method is widely employed to estimate infectious dose (ID50) in virology, bacterial neutralization assays, and vaccine research. It is appreciated for its simplicity and minimal data requirements. Limitations include sensitivity to the distribution of responses and to the assumption of linear interpolation between bracketing dilutions. When data are sparse or highly variable, alternative methods such as the Spearman–Kärber or probit/logit approaches may be preferred.

History

The method is named after Leonard J. Reed and H. Muench, who described it in 1938 as a simple technique for estimating 50% endpoints from titration data.