Also recommended in Q10 is: "... a written agreement between the contract giver and contract acceptor." This agreement should
include the acceptable quality limit (AQL) and limited quantity (LQ) limits for incoming sampling plans as well as the usual
specification methods and acceptance criteria. Data collected in-coming and in-process can be used to determine compliance
with a contract agreement. Per Q10, "Throughout the product lifecycle, companies are encouraged to evaluate opportunities
for innovative approached to improve product quality" (1).
There are many ways, statistically, to achieve this goal. Trending, designed experiments, variability reduction, and design
space are just some of the tools that can be used to make process improvements.
Many of the terms in ICH Q10 imply trending of critical parameters and attributes. It is a given that this must be done. Q10
states: "An effective monitoring system provides assurance of the continued capability of processes and controls to produce
a product of desired quality and to identify areas for continual improvement" (1).
Process capability is measured by comparing the variability of the product/process to the width of the specification range.
This comparison can best be achieved using statistical tolerance intervals because they take into account the sample size
where Cpk and Ppk do not. Per Q10, "Identify sources of variation affecting process performance and product quality for potential
continual improvement activity to reduce or control variation" (1).
Some Six Sigma programs have gotten a poor reputation in certain circles because of a single-minded focus on saving money
as opposed to giving equal consideration to improving quality and reducing variation. It is the author's opinion that management
needs to give equal attention and resources to both. As Q10 calls for, "Proposed changes should be evaluated by expert teams
contributing the appropriate expertise and knowledge from relevant areas (e.g., Pharmaceutical Development, Manufacturing,
Quality, Regulatory Affairs and Medical), to ensure the change is technically justified" (1). The company's statistics department
or a statistician should be included in the team.
Many statements in ICH Q10 have important implications for the correct and consistent use of statistics in the day-to-day
implementation of pharmaceutical quality systems. Addressing these harmonized recommendations proactively and in context can
help to strengthen one's quality system and thereby reduce rejects and recalls.
Lynn D. Torbeck is a statistician at PharmStat Consulting, 2000 Dempster, Evanston, IL 60202, tel. 847.424.1314, LDTorbeck@PharmStat.com
References and notes
1. ICH, Q10 Pharmaceutical Quality System (2008).
2. ICH, Q8 Pharmaceutical Development (2009).
3. ICH, Q9 Quality Risk Management (2005).
4. L. Torbeck, Pharm. Technol.
35 (10) 46–47 (2011).
5. Note: Other definitions of Engineering Control exist in other industries.
6. Note: It is common practice to use only one to three of the eight Western Electric rules for a given control chart. It
is counterproductive to use more than three rules at a time.