A Simple Capability Index of Product Shelf Life & Omission of Statistical Analysis for Stability Data with Small Total Degradation and Variability Relative to Distance to Specification Limit(s)

For products with small total degradation and variability relative to the distance to specification limit(s), this paper proposes a simple, range-based capability index to provide assurance that the requested shelf life will be supported according to International Conference for Harmonisation stability guidelines with justification for omission of formal statistical analysis. The tool provides objective support to subjective visual data assessment and requires no regression or otherwise sophisticated analysis, only a 1-step calculation involving the minimum and maximum data values, and the specification limit(s). This approach is applicable to long-term stability data from 3 - 15 batches with one response measurement at each of the recommended time points (month 0 and every 3, 6, and 12 months respectively for the 1st, 2nd, and subsequent years) out to a requested shelf life of 12, 18, 24, 36, 48, or 60 months, 1- and 2-sided 95% confidence intervals, and linear stability trends. The methodology should not be used if the stability context / data have any of the following characteristics: confidence coefficient, number of batches, time points, or requested shelf lives other than that listed above, nonlinear trends, missing data, multiple data values from the same batch at an individual time point, two or more batches with data extending out to different endpoints, the need for either computation of extrapolation beyond the data or estimation of the longest supportable shelf life. For these excluded situations, a formal statistical analysis or comprehensive written justification for its omission is needed.