Zero Acceptance Number Sampling Plans and the FDA

Question

There has been some debate over using the MIL-STD-1916 acceptance sampling plan over the ANSI/ASQ Z1.4-2003 (R2013) sampling plans.  The opinion is that the ANSI/ASQ Z1.4-2003 (R2013) is outdated and no longer an acceptable method of determining a qualification sample plan and the MIL-STD-1916 should be used in place of ANSI/ASQ Z1.4-2003 (R2013). Do you have information around this debate over which sampling plans are acceptable by the FDA?

Answer

FDA does not (and can not) tell you what sampling plan is to be used.  The FDA requirement is that the plan be statistically valid.  As long as you follow the regulation, you are meeting FDA requirements.

In medical device manufacturing the key point is to have the plan accept on zero defectives.  This point is not FDA but legalese.  It is based on past lawsuits.  The plan “Zero Acceptance Number Sampling Plans” by Nicholas L. Squeglia (available from ASQ) has been widely adopted for this reason.

ANSI/ASQ Z1.4 in not outdated and continues to be widely used.  It is the American National Standard Institute (ANSI) version of MIL-STD-105 which the government discontinued maintaining, allowing ANSI to maintain it along with many, many other MIL-STD’s as a government cost reduction.

MIL-STD-1916 can be used but it is not widely used because of its difficulty and practical use.

James Werner

Posted in FDA regulated industries, Other, Z1.4 & Z1.9 - Sampling | Tagged , | Leave a comment

AQL Clarifications

Question

I am confused about the values used for AQLs. For example in Table II-A the AQL values range from 0.010 to 1000. Where do these values come from and what do they mean?

The table states, “AQLs, in Percent Nonconforming Items and Nonconformities per 100 Items .” At first I thought the values were percentages, but how can you have more than 100, as in 100%, as the values go up to 1000? Also how can there be more than 100 nonconformities per 100 items, unless one part can have multiple nonconformities?

Just looking for clarification on the AQL numbers, what they mean, and how to interpret them.

Answer

Let’s start with the definition of Acceptable Quality Level (AQL).  From Z1.4, the AQL is the quality level that is the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling.  Although individual lots with quality as bad as the AQL can be accepted with fairly high probability, the designation of an AQL does not suggest that this is necessarily a desirable quality level. The AQL is a parameter of the sampling scheme and should not be confused with a process average which describes the operating level of a manufacturing process. It is expected that the product quality level will be less than the AQL to avoid excessive non-accepted lots.

The columns with percentages greater than 100% should not be included in the standard, but remain as indication of how to interpret lots where the entire sample is defective.  It has some statistical relevance with use of the switching rules, but for the general practitioner, it should be ignored.

Hope this helps.

Steven Walfish

Posted in Other, Sampling, Z1.4 & Z1.9 - Sampling | Tagged , | Leave a comment

DPMO

Question

My question concerns the process performance metric DPMO (defects per million opportunities). I want to use this to quantify a particular supplier’s performance. My question is, is the number of defects referred to in the calculation the number of defects produced by the supplier (in which case it would involve data I don’t have access to), or is it the number of defects experienced by the customer (which is us)? I of course can count the number of defects we receive from the supplier, but if this metric is supposed to be based on the number of defects produced by an organization, I would have no way of knowing how many defects are produced by the supplier’s process, but contained within the supplier’s facility. My hope is to be able to characterize the supplier’s process performance in terms of sigma level.
Answer

The DPMO metric is not usually considered a point estimate of the true percent defective in the lot (either at the supplier or customer site).  It is a relative performance metric used to equate the observed percent defective from a sample to defective units per million opportunities.  If a supplier culls out all the defective units before shipping to you (i.e. perfect inspection system), your internal DPMO would be 0, even if the supplier DPMO is high. If your goal is to characterize the supplier’s process performance in terms of sigma level, you would need their data, as the data you collect internally is just an estimate for the average outgoing quality from the supplier and not their process performance.

Steven Walfish

Posted in Other, Sampling, Six Sigma | Tagged , , | Leave a comment

Document Revision Criteria

Question

Is there any criteria available for the frequency of document revision in ISO 9001 or ISO 13485?  Some organization don’t revise the documents for a period of more than 2-3 years.  The reason provided by the organization is that there were no changes during this period. Do ISO standards mandate the revision of documents within a certain time frame? Can we treat this as non-compliance, if the documents are not revised over a period of 2-3 years ?
Answer

There are no criteria nor a requirement for document revision in ISO 9001:2015, 7.5.

ISO 13485:2016, 4.2.4, states, “review, update as necessary and re-approve documents.” This leave the review to the discretion of the organization.

Thus, there is no mandatory review frequency and no non-conformance if documents are not revised within a determined time frame.  ISO 13485 does require a review, however. But, the frequency of the review is not mandated.

George Hummel

Posted in ISO 13485 - Medical Devices, ISO 9001 - Quality Management Systems, Other | Tagged , | Leave a comment

Verification or Calibration?

Question

There is a second part to 7.6 para “a” which reads; “where no such standards exist, the basis used for calibration or verification shall be recorded.” It is clear for shops that are complying to the ISO 9001:2008(E) we need to have measurement standards traceable to international or national measurement standards. My question has to do with cylindrical plug gages that are used at the machines to verify manufactured print dimensions. The pins/plug gages are not sent out at intervals for calibration however, they are compared to a traceable measurement standard before being issued to the manufacturing area. We consider these gages to be calibrated “as used ” and we do not record the intial actual size of the pins/plug gage but issue it only on the basis that the size was verified against a traceable measurement standard. Are we required per Para 7.6 to record the actual size of the pins/plug gages?

Answer

Thank you for your question.  What you are describing is verifying prior to use, rather than calibration.    If the rings or other standards being used to check these plug gauges each day are properly calibrated and traceable to national standards, you are compliant with ISO 9001:2015.  If you are registered to AS 9100 or TS 16949, stricter requirements will apply and you may not be meeting those requirements for recording variable results of calibration.

Denis Devos, P.Eng
A Fellow of the American Society for Quality
Devos Associates Inc.
(519) 476-8951
www.DevosAssociates.com

Posted in ISO 9001 - Quality Management Systems, Other | Tagged | Leave a comment

Clauses 8.4.1 and 8.4.2 in 9001

Question

The insurance company I am temporarily helping on quality is limiting its ISO 9001 certified perimeter to the administration of contracts and claims.
With regard to clauses 8.4.1 and particularly 8.4.2 of ISO 9001:2015, should the other internal entities of the company (.i.e HR, IT, Sales Dpt, …) absolutely necessary but outside of the perimeter be considered exactly like external providers – just like a provider of IT, for instance – or should they be considered as internal providers with a limited control of their contribution to the QMS through a simplified SLA? Of course, SLAs will be put in place in order to secure the relationship of these internal entities with the perimeter.

I thank you in advance for your help/interpretation of clauses 8.4.1 and 8.4.2 applied to the case submitted.

Answer

Thank you for your question.   Yes, that is an appropriate interpretation, but let me add three comments.

Firstly, recognize that your support functions are captive within your organization and therefore not subject to all of the same conditions that would be imposed on an outside service provider.   For example, you can’t stop doing business with them if you are not happy with their service.  I like your idea for an SLA – keep it simple, but outline your requirements and expectations for their support services.

Secondly, use your process approach (clause 4.4) to define the boundaries of your QMS and how those other external departments interface with you.  This will be helpful in helping your team and others to understand the relationship between your QMS and the rest of the organization.

Thirdly, take advantage of the Context of the Organization analysis (clause 4.1) to further explore those relationships and that will help to determine the level of control you require over those support functions.

Denis Devos, P.Eng
A Fellow of the American Society for Quality
Devos Associates Inc.
(519) 476-8951
www.DevosAssociates.com

Posted in ISO 9001 - Quality Management Systems, Other | Tagged , | 1 Comment

“Shall Be Determined” in 9001

Question

Many of the Quality Management Systems requirements in the ISO 9001: 2015 manual include the verbiage “shall be determined.”  I need to be sure that I understand exactly what this means in this context.  For example, “4.4  QMS and its processes 4.4.1 a)  The inputs required and the outputs expected of the QMS processes are determined.”   Does this mean that there should be process or work instruction written describing this?  Does it mean that there should be documentation showing the development of this information?

Answer

Thank you for your question.  It might be useful to look at the definition of the word determine.  According to the Oxford Dictionary:  Determine means to “Ascertain or establish exactly be research or calculation”, Merriam Webster has a similar definition:  “to find out about or come to a conclusion about by investigation, reasoning, or calculation.

Now to your question.  There does not need to be a procedure about how things are determined.  The output, or the determination itself, will serve as evidence that you did it.  But determine things in an honest way.  You and your CB auditor will assess the reasonableness of your determinations based on the context of your organization.  For example, if you are a hospital, and you “determine” that surgeons do not need to wash their hands, you should be subject to a nonconformance for getting that wrong.    In your example, taken from clause 4.4, the best way to do this is to create a flowchart(s) showing a series of process steps and their interactions.  The arrows in and out of each box along with explanatory text, will demonstrate that you have determined the inputs and outputs of each process step.

Denis Devos, P.Eng
A Fellow of the American Society for Quality
Devos Associates Inc.
(519) 476-8951
www.DevosAssociates.com

Posted in ISO 9001 - Quality Management Systems, Other | Tagged , | Leave a comment