Acceptable Quality Level (AQL) in Pharmaceuticals

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What is AQL

AQL’ stands for ‘Acceptance Quality Limit’, and is defined as the “quality level that is the worst tolerable” in ISO 2859-1. It decides on the maximum number of defective units, beyond which a batch is rejected. Importers usually set different AQLs for critical, major, and minor defects. Most Asian exporters are familiar with this type of setting.

AQL

For example: “I want no more than 1.5% defective items in the whole order quantity, on average over several production runs with that supplier” means the AQL is 1.5%.

In practice, three types of defects are distinguished. For most consumer goods, the limits are:

  • 0% for critical defects (totally unacceptable: a user might get harmed, or regulations are not respected).
  • 5% for major defects (these products would usually not be considered acceptable by the end user).
  • 0% for minor defects (there is some departure from specifications, but most users would not mind it).

These proportions vary in function of the product and its market. Components used in building an airplane are subject to much lower AQL limits.

Note that this tool is used mostly during final outgoing inspections (when the products are ready to be shipped out), and sometimes during production (when the number of products is sufficient to have an idea of the batch’s average quality).

The “AQL tables” are statistical tools at the disposal of buyers (for product inspections). They are an industry standard. Most suppliers involved in international trade are familiar with it.

The concept of Acceptable Quality Level is taken from ISO 2859-1 – Sampling Procedure for Inspection. This is statistical tool that helps the buyer in product inspection.

Determination and implementation of Acceptable quality limit in pharmaceuticals

“AQL Tables” determine two key elements:

  1. How many samples should be picked and analyzed, among a batch of product or parts?
  2. Acceptance Criteria to reject or approve the batch

AQL tables for product inspections

These statistical tables are fundamental tools for preparing a sampling plan for a random product inspection. They give you the number of samples to inspect, and the maximum numbers of defects that is allowed.

The first table gives you the code letter for sampling. In this example, if the batch to check contains 5,000 pcs, and if you choose level II (which is chosen by default for most inspections), the letter is L.

AQL-table-1

The second table (for normal severity) gives you the useful information. The letter L means 200 samples must be checked. If you select the limits as 2.5% for major defects and 4.0% for minor defects, you reject the batch if you find more than 10 major and/or more than 14 minor defects.

AQL-table-2

How to use the AQL Tables?

Table A

table1

Table B

table2

How to use the AQL Tables?

Let’s take a hypothetical inspection of a 30 000 pieces lot.

The Table A, under the column level II, gives us the letter M, which corresponds in the table B to a sampling size of 315 pieces to inspect. The usual AQL used by people is generally: 0 / 2.5 / 4 for Critical / Major / Minor defects. For the letter M, 315 pieces to inspect, the column 2.5 for defects gives us two numbers: 14 & 15. Thus Among a sampling size of 315 pieces inspected, the maximum number of major defects authorized is 14.

If we find 15 major defects, you should reject your shipment and / or perform defect sorting, ask for a re-work of the production or ask for a replacement of your production. Then you should get your shipment re-inspected a second time.

In the contrary, for these 315 pieces inspected, if we find less than 15 defective items, this means that there are 95% chances to have less than 5% (15/315) defects in the whole inspected lot.

Using Acceptable Quality Level in pharmaceuticals can help to meet the international standards for pharmaceuticals inspection. A sampling plan can be created for pharmaceutical finished product using these AQL tables.

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