Statistical Solutions: Visual Inspection Goes Viral - Pharmaceutical Technology

Latest Issue
PharmTech

Latest Issue
PharmTech Europe

Statistical Solutions: Visual Inspection Goes Viral
To properly inspect based on measurement, a reference standard is crucial for comparison.


Pharmaceutical Technology
Volume 34, Issue 9, pp. 34-35

Inspection in action

Consider, for example, a manufacturing company that was using an industry standard 100% visual-inspection program to review finished vials. The program had been in place for several years and results of the visual inspections for spots on stoppers had typically been in the 2–5% range. However, over the course of several weeks, the cull rate escalated from 5% to more than 20%.

Alarmed, the quality unit conducted an investigation, but was unable to identify a clear reason for the dramatic increase. The inspectors and environment had not changed. Puzzled, the company brought in a consultant to assist with the investigation.

The consultant pointed out a fundamental measurement rule and asked, "Where is the standard for spots on stoppers?" The reply was, "There is none. Each inspector uses their best judgment." The consultant responded, "Without a standard, there is no basis for measurement."

Essentially, each inspector was using his own floating scale without any reference point. As the inspection continued, one inspector pointed out that he found a few more spots on the vials than usual. Sensitized to this information, the other inspectors became more vigilant and began to find more spots themselves. As word spread, the inspectors became hypersensitive, finding more and more spots as each lot was inspected until they were identifying more than 20% rejects.

Some identified spots were so small that the supervisors and managers could not see them even when pointed out by the inspectors. Without a standard for reference, any perceptible dot became a defect. A team discussion led to a defined specification: a spot below a certain size was not to be counted as a defect.

Summary

The company described in the above example soon adopted the TAPPT dirt estimation chart (1) as its reference standard. Each operator was given an original card for use during inspection. If any questions arose, the inspectors could compare potential defect spots to the chart and also review them with the supervisor.

Within one working shift, the defect level for spots on stoppers dropped back to the 2–5% range. The lesson learned: measurement is a comparison to a reference standard.

Lynn D. Torbeck is a statistician at Torbeck and Assoc., 2000 Dempster Plaza, Evanston, IL 60202, tel. 847.424.1314,
, http://www.torbeck.org/.

Reference

1. Dirt and Size Estimation Charts, http://www.tappi.org/Standards-TIPs/Dirt-Size-Charts.aspx, accessed Aug. 19, 2010.


ADVERTISEMENT

blog comments powered by Disqus
LCGC E-mail Newsletters

Subscribe: Click to learn more about the newsletter
| Weekly
| Monthly
|Monthly
| Weekly

Survey
What role should the US government play in the current Ebola outbreak?
Finance development of drugs to treat/prevent disease.
Oversee medical treatment of patients in the US.
Provide treatment for patients globally.
All of the above.
No government involvement in patient treatment or drug development.
Finance development of drugs to treat/prevent disease.
28%
Oversee medical treatment of patients in the US.
9%
Provide treatment for patients globally.
9%
All of the above.
41%
No government involvement in patient treatment or drug development.
13%
Jim Miller Outsourcing Outlook Jim MillerCMO Industry Thins Out
Cynthia Challener, PhD Ingredients Insider Cynthia ChallenerFluorination Remains Key Challenge in API Synthesis
Marilyn E. Morris Guest EditorialMarilyn E. MorrisBolstering Graduate Education and Research Programs
Jill Wechsler Regulatory Watch Jill Wechsler Biopharma Manufacturers Respond to Ebola Crisis
Sean Milmo European Regulatory WatchSean MilmoHarmonizing Marketing Approval of Generic Drugs in Europe
FDA Reorganization to Promote Drug Quality
FDA Readies Quality Metrics Measures
New FDA Team to Spur Modern Drug Manufacturing
From Generics to Supergenerics
CMOs and the Track-and-Trace Race: Are You Engaged Yet?
Source: Pharmaceutical Technology,
Click here