Comparison of D10-value accuracy by the limited Spearman-Karber procedure (LSKP), the Stumbo-Murphy-Cochran procedure (SMCP), and the survival-curve method (EN).

Abstract

The decimal reduction time (D10) may be determined by any of several methods, including the limited Spearman-Karber procedure (LSKP), the Stumbo-Murphy-Cochran procedure (SMCP), and the survival-curve method (EN). The International Organization for Standardization (ISO) endorses the LSKP and the EN. Most Japanese and German industries utilize the SMCP and the EN for calculation of the D value. A presentation at an ISO meeting suggested that the SMCP was less accurate than the LSKP, and the ISO recommended abandoning the SMCP. The paper concerning the accuracy comparison among these methods has not been published. Therefore, in order to examine whether the SMCP was truly inferior to the LSKP, the Japanese delegates to the ISO compared the accuracies of D10 values obtained with these methods by simulation and in experimental procedures using a biological indicator (BI) and a biological indicator evaluator resistometer (BIER) with ethylene oxide gas sterilization. The results indicate that the SMCP was not consistently less accurate than the LSKP in determining D10.