How to Investigate Out Of Specification(OOS) Test Results….???( USFDA Phase -I)

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How to Investigate Out Of Specification(OOS) Test Results….??? ( USFDA Phase -I)

Out Of Specification(OOS) :-  The all test results which goes outside the specification or acceptance criteria established in Drug Dossiers, Drug Master files, Its official Pharmacopeias, Or the manufacturer comes Under Out of Specification(OOS).


What USFDA guideline says about Investigation of Out of Specification.?


The term OOS results includes all test results that fall outside the specifications or acceptance criteria established in drug applications, drug master files (DMFs), official compendia, or by the manufacturer. The term also applies to all in-process laboratory tests that are outside of established specifications.

This guidance applies to chemistry-based laboratory testing of drugs regulated by CDER. It is directed toward traditional drug testing and release methods. These laboratory tests are performed on active pharmaceutical ingredients, excipients and other components, in-process materials, and finished drug products3 to the extent that current good manufacturing practice (CGMP) regulations (21 CFR parts 210 and 211) and the Federal Food, Drug, and Cosmetic Act (the Act) (section 501(a)(2)(B)) apply. The principles in this guidance also apply to in-house testing of drug product components that are purchased by a firm. This guidance can also be used by contract firms performing production and/or laboratory testing responsibilities. Specifically, the guidance discusses how to investigate OOS test results, including the responsibilities of laboratory personnel, the laboratory phase of the investigation, additional testing that may be necessary, when to expand the investigation outside the laboratory, and the final evaluation of all test results.



Regulations require that an investigation be conducted whenever an OOS test result is obtained (§ 211.192).6 The purpose of the investigation is to determine the cause of the OOS result. The source of the OOS result should be identified either as an aberration of the measurement process or an aberration of the manufacturing process. Even if a batch is rejected based on an OOS result, the investigation is necessary to determine if the result is associated with other batches of the same drug product or other products. Batch rejection does not negate the need to perform the investigation. The regulations require that a written record of the investigation be made, including the conclusions and follow-up (§ 211.192). To be meaningful, the investigation should be thorough, timely, unbiased, well-documented, and scientifically sound. The first phase of such an investigation should include an initial assessment of the accuracy of the laboratory’s data. Whenever possible, this should be done before test preparations (including the composite or the homogenous source of the aliquot tested) are discarded. This way, hypotheses regarding laboratory error or instrument malfunctions can be tested using the same test preparations. If this initial assessment indicates that no meaningful errors were made in the analytical method used to arrive at the data, a full-scale OOS investigation should be conducted. For contract laboratories, the laboratory should convey its data, findings, and supporting documentation to the manufacturing firm’s quality control unit (QCU), who should then initiate the full-scale OOS investigation.


  1. Responsibility of the Analyst


The first responsibility for achieving accurate laboratory testing results lies with the analyst who is performing the test. The analyst should be aware of potential problems that could occur during the testing process and should watch for problems that could create inaccurate results.

In accordance with the CGMP regulations in § 211.160 (b)(4), the analyst should ensure that only those instruments meeting established performance specifications are used and that all instruments are properly calibrated.

Certain analytical methods have system suitability requirements, and systems not meeting these requirements should not be used. For example, in chromatographic systems, reference standard solutions may be injected at intervals throughout chromatographic runs to measure drift, noise, and repeatability. If reference standard responses indicate that the system is not functioning properly, all of the data collected during the suspect time period should be properly identified and should not be used. The cause of the malfunction should be identified and, if possible, corrected before a decision is made whether to use any data prior to the suspect period.

Analysts should check the data for compliance with test specifications before discarding test preparations or standard preparations. When unexpected results are obtained and no obvious explanation exists, test preparations should be retained, if stable, and the analyst should inform the supervisor. An assessment of the accuracy of the results should be started immediately.

If errors are obvious, such as the spilling of a sample solution or the incomplete transfer of a sample composite, the analyst should immediately document what happened.

Analysts should not knowingly continue an analysis they expect to invalidate at a later time for an assignable cause (i.e., analyses should not be completed for the sole purpose of seeing what results can be obtained when obvious errors are known).


  1. Responsibilities of the Laboratory Supervisor

Once an OOS result has been identified, the supervisor’s assessment should be objective and timely. There should be no preconceived assumptions as to the cause of the OOS result. Data should be assessed promptly to ascertain if the results might be attributed to laboratory error, or whether the results could indicate problems in the manufacturing process. An immediate assessment could include re-examination of the actual solutions, test units, and glassware used in the original measurements and preparations, which might provide more credibility for laboratory error hypotheses.

The following steps should be taken as part of the supervisor’s assessment:

  1. Discuss the test method with the analyst; confirm analyst knowledge of and performance of the correct procedure.

  2. Examine the raw data obtained in the analysis, including chromatograms and spectra, and identify anomalous or suspect information.

  3. Verify that the calculations used to convert raw data values into a final test result are scientifically sound, appropriate, and correct; also determine if unauthorized or unvalidated changes have been made to automated calculation methods.

  4. Confirm the performance of the instruments.

  5. Determine that appropriate reference standards, solvents, reagents, and other solutions were used and that they met quality control specifications.

  6. Evaluate the performance of the test method to ensure that it is performing according to the standard expected based on method validation data and historical data.

  7. Fully document and preserve records of this laboratory assessment.

The assignment of a cause for OOS results will be greatly facilitated if the retained sample preparations are examined promptly. Hypotheses regarding what might have happened (e.g. dilution error, instrument malfunction) should be tested. Examination of the retained solutions should be performed as part of the laboratory investigation.



  • Solutions can be re-injected as part of an investigation where a transient equipment malfunction is suspected. Such hypotheses are difficult to prove. However, reinjections can provide strong evidence that the problem should be attributed to the instrument, rather than the sample or its preparation.

  • For release rate testing of certain specialized dosage form drugs that are not destroyed during testing, where possible, examination of the original dosage unit tested might determine whether it was damaged during laboratory handling in a way that affected its performance. Such damage would provide evidence to invalidate the OOS test result, and a retest would be indicated.

  • Further extraction of a dosage unit, where possible, can be performed to determine whether it was fully extracted during the original analysis. Incomplete extraction could invalidate the test results and should lead to questions regarding validation of the test method.

It is important that each step in the investigation be fully documented. Laboratory management should ascertain not only the reliability of the individual value obtained, but also the significance these OOS results represent to the laboratory quality assurance program. Laboratory management should be especially alert to developing trends. As part of an effective quality system, a firm’s upper management should appropriately monitor these trends and ensure that any problematic areas are addressed.

Laboratory error should be relatively rare. Frequent errors suggest a problem that might be due to inadequate training of analysts, poorly maintained or improperly calibrated equipment, or careless work. Whenever laboratory error is identified, the firm should determine the source of that error and take corrective action to prevent recurrence. To ensure full compliance with the CGMP regulations, the manufacturer also should maintain adequate documentation of the corrective action.

In summary, when clear evidence of laboratory error exists, laboratory testing results should be invalidated. When evidence of laboratory error remains unclear, a full-scale OOS investigation should be conducted by the manufacturing firm to determine what caused the unexpected results. It should not be assumed that OOS test results are attributable to analytical error without performing and documenting an investigation. Both the initial laboratory assessment and the following OOS investigation should be documented fully.

Reference :-

Guidance for Industry

Investigating Out-of-Specification (OOS)
Test Results for
Pharmaceutical Production


28 thoughts on “How to Investigate Out Of Specification(OOS) Test Results….???( USFDA Phase -I)”

  1. Omg! Great post I had no idea this was something I had to consider. I have to re-read the whole post to fully understand it and have all this information present.
    Thank you so much for sharing.

  2. This is a highly detailed post that will be useful for some people. I prescribe medications so it is great to understand the process of insuring safety.

  3. As someone who has a few medicine prescriptions, it is good to know what goes on behind the scenes in the pharmaceutical world. This post was very informative about how testing takes place.

  4. You’ve presented an abundance of information and outlined so many details pertinent to FDA approval of pharmaceuticals. I’m sure this information will benefit those in the industry!

  5. I work in the clinical research field, but mainly on Phase 2 and 3 trials. Always been curious about phase 1 trials. Thanks for sharing!

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