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Investigating for Failures

The FDA and other regulatory agencies consider the integrity of laboratory data to be an integral part of the drug manufacturing process. Deficiencies of out-of-specification (OOS) investigations continue to be the major cause of warning letters in the pharmaceutical industry.

by Violet M. Carvalho
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The FDA and other regulatory agencies consider the integrity of laboratory data to be an integral part of the drug manufacturing process.1,2 Deficiencies of out-of-specification (OOS) investigations continue to be the major cause of warning letters in the pharmaceutical industry. The regulatory agencies require that OOS, out-of-trend (OOT), or aberrant results be investigated.3 An effective and compliant quality management system will ensure thorough, timely, unbiased, well-documented, scientifically sound investigations for OOS, OOT, and aberrant results, which will ensure, if a root cause can be assigned, the implementation of appropriate corrective and preventative actions. The challenge for many firms is having a clearly outlined and well-organized process that is well understood by analysts, supervisors, and manufacturing personnel and that provides for clear, concise, complete documentation. A lack of consistency in the approaches to investigations and root-cause analyses also leads to weak, inconclusive investigations.

The firm’s procedure for failure investigations should discuss the types of errors that may arise and how to deal with them, describe how to investigate failures, and cover timeliness of assessments, including the following: scope, roles and responsibilities, definitions, investigation procedure (phases of the investigation), documentation, corrective and preventative action, and trend analysis.

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The focus of this article is an OOS investigation; however, the principles are applicable to all analytical laboratory investigations.


The scope of the investigation procedure should clearly state when the investigation is required, and define OOS, OOT, and aberrant results.

OOS results are most often generated due to laboratory or manufacturing-related errors, the setting of inappropriate specifications,4, or poor method development.5,6 OOT results may be within specification but show significant variation from historical results. Aberrant results include unexpected variability in analytical results and system suitability failures. For example, % impurity value of 0.3 for early-phase API lots did not meet criteria of 0.2, which was set based on research lots of 100g quantities; % assay value of 96.0 met the specification of 95.0-105.0 but was lower than historical values of 99.7, 99.4, 99.5, 98.9, and 99.5; and the solvent standard weight in a gas chromatographic headspace was very small, such that the % RSD criteria for the standards were not met.

The scope should also indicate the analytical results to which the procedure is applicable: release test results for components, intermediates, drug substance, and drug products; stability test results; reference standards; method transfers; and method validations. Research samples, in-process checks, and method development are not within the scope.

Roles and responsibilities

The roles and responsibilities of the testing unit—the analyst and supervisor in Quality Control and Quality Assurance (QA)—should be outlined. The analysts should ensure that they are trained on the test method, are aware of the potential problems that can occur during the testing process, and watch for problems that could contribute to inaccurate results. Process flow charts and chromatographic profiles unique to the material facilitate the analyst’s understanding of the testing. The supervisor is responsible for the objective, timely assessment of the investigation to determine if the results might be attributed to laboratory error or indicate problems in manufacturing, a poorly developed or poorly written test method, or inappropriate specifications. QA is responsible for the review, approval, and tracking of the investigation.


Terms used in the investigation procedure, such as OOS, OOT, and aberrant result, should be clearly defined. The differences between retest and repeat testing, and corrective and preventative action (CAPA), should be described.

Investigation procedure

The investigation procedure should describe the phases of the investigation and recommended timing for completion of each phase. The investigation consists of the initial assessment, laboratory supervisor’s assessment, practical laboratory investigation, retesting, and conclusion of the investigation. Refer to the OOS investigation flowchart.

The initial assessment should focus on determining the assignable cause, so that laboratory error is confirmed or ruled out. The analyst should confirm the accuracy of test results, identify known errors, and carefully consider observations made during testing, to provide possible insight into the failures. The analyst should also check the data for compliance with test specifications before discarding test preparations. Checklists can be used to aid in identification of these errors (e.g., verification of identity of samples, standards, reagents, and correct preparation of samples) and have the advantage of maintaining consistency in initial assessments. The analyst is responsible for initiating and documenting the investigation, and reporting the occurrence to the laboratory supervisor and QA within a specified time frame.

The laboratory supervisor’s assessment should be objective and timely and include a review of the supporting documentation and a discussion with the analyst to confirm the analyst’s knowledge of and performance of the correct test method. Potential causes of the suspect result should be identified and a plan documented to identify and confirm or rule out a potential cause by conducting a practical laboratory investigation.

QA is responsible for assigning a unique identifier to the investigation at the outset, reviewing and tracking the investigation, and approving the completed investigation and CAPA.

Conducting the practical laboratory investigation

The purpose is to confirm or determine the assignable cause through additional laboratory work. The documented plan should be executed and the results evaluated. It must be noted that the results obtained from the practical investigation are not “reportable results” and are for the purpose of the investigation only. Examination of the retained standard and sample solutions should be performed as part of the investigation.

If an assignable cause is identified, then the original suspect result is invalidated. The error is corrected, results from all affected samples are assessed, and the test is repeated. The result from the repeat test is reported and the investigation concluded. When evidence of laboratory error remains unclear, a full-scale investigation should be conducted.

Expansion of investigations

When the initial assessment does not determine that laboratory error caused the failure and test results appear to be accurate, a full-scale investigation should be conducted. Dependent on the specifics of the failure investigation, the investigation might consist of review of the manufacturing process, and stability results of the lot for previous time points and of other lots, if any. Results of other tests performed on the lot should also be assessed. The investigation might also include additional laboratory testing. The goal is to determine the root cause, followed by implementation of corrective actions prior to any retests of the lot. The longterm action should be a preventative action to decrease the incidence of the error or failure.

Review of manufacturing process or process external to the originator laboratory should involve affected departments, and an evaluation by the multidisciplinary team should be coordinated by QA. If this part of the investigation confirms the OOS result and identifies the root cause, the investigation may be completed.

Retesting is performed to confirm or not confirm the test result. A full-scale investigation may include additional laboratory testing when the initial assessment and practical laboratory investigation fail to clearly identify the cause of the suspect results. The firm’s procedure should clearly state the number of samples and replicates to be used in the retest, prior to start of the retest. The criteria for evaluating the results should also be predefined in the plan. This provides an unbiased approach and preempts the perception of testing into compliance.

The procedure should state what results are to be reported. If an assignable cause has been identified, the original results should be invalidated and the retest results reported. If an assignable cause is not identified, suspect results should not be invalidated. There is no justification for rejecting a suspect result and accepting a passing result. All test results, both passing and suspect, should be reported.

Conclusion of investigation is the final step after an assessment of all the supporting information. QA then dispositions the material.


The investigation procedure should describe what information needs to be documented: the reason for the investigation, including what happened, when, and where; initial assessment including checklists; the laboratory supervisor’s assessment; details of the investigation plan; and executed practical investigation, retests, and conclusion of the investigation. The procedure should clearly state where the information is to be recorded and delineate at what stage reviews and approvals by the laboratory supervisor and QA are required.

Root causes and corrective and preventative action

Many firms will note the root cause as “analyst error” without drilling down to the actual root cause, thus missing the opportunity to implement a more relevant preventative action and build a robust, quality laboratory system.

The goal of the investigation is to determine a root cause. This will in turn trigger corrective actions to address the immediate issue, and preventative actions that are aimed at reducing the frequency of failures and/or errors in the long term; for example, the failure of an assay is tracked to an incorrect amount of material weighed. Was the weighing of the incorrect amount due to poor analytical technique? Was the analyst not trained in basic laboratory skills? The corrective action would be to ascertain that the analyst was proficient in pipette use, prior to reweighing the sample. In this case, the preventative action might be to evaluate the training program for laboratory personnel. Or was the pipette out of tolerance? What then was the frequency of calibration? Was the pipette subjected to heavy daily use? The corrective action to address the immediate issue would be to use another pipette that is in calibrated status. The preventative action would be to determine if the pipette has heavy daily use, and to increase the frequency of calibration to every six or three months, to better ensure that the pipette was “within tolerance.”

Trend analysis

A periodic review of trend analysis provides invaluable information for improvements to the laboratory system. It highlights trends in failure investigations by instrumentation, method, analyst, and product.


In conclusion, the best practice, undoubtedly, is to minimize the generation of failures. Careful description of test methods and reportable values, including appropriate system suitability parameters, can help prevent test result failures and anomalies. Scientifically sound test method development and validation approaches, a well-designed instrument/equipment qualification, and a robust metrology program, combined with qualification and training of analysts in basic laboratory skills and analytical techniques—and unambiguous, well-written test methods along with a clear and comprehensive investigation procedure—will help minimize errors and failures.


  1. 21 Code of Federal Regulations Part 211 - Current Good Manufacturing Practice for Finished Pharmaceuticals, April 1996.
  2. 21 Code of Federal Regulations Part 58 - Good Laboratory Practice for Non- Clinical Laboratory Studies, April 2010.
  3. Guidance for Industry Investigating Out of Specification (OOS) Test Results for Pharmaceutical Production, October 2006.
  4. ICH Q6A Specifications: Test Procedures and Acceptance Criteria for New Drug Substances and New Drug Products: Chemical Substances, December 2000.
  5. ICH Q2A Text on Validation of Analytical Procedures, March 1995.
  6. ICH Q2B Validation of Analytical Procedures: Methodology, May 1997.

Violet M. Carvalho, director, Quality Control, Arena Pharmaceuticals, can be reached at or by phone at 858-453-7200 ext 1734.