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The page below is a sample from the LabCE course Understanding and Utilizing Lean and Six Sigma in the Histology Laboratory. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Applying Root Causes to Correcting and Preventing Process Defects

Process correction

Corrective action metrics or plans are used to eliminate an identified problem by proposing appropriate solutions. The goal of a corrective action plan is to provide a standardized method which would help in assessment of a defect and provide the recommended course of action for correction. Corrective actions are built on an accurate identification of the root causes of various problems which need improvement, and one of the main reasons why root cause analysis is vital to creating action-oriented protocols for critical to quality defects. An effective corrective plan accurately identifies root causes, and then provides a clear and standardized protocol to be followed to halt and correct errors in a process at the earliest point possible.

The ideal solution to errors and defects is of course to devise methods which prevent them from occurring altogether. Error prevention or Error-proofing is known as" Poka-Yoke" in Japan. Polka The word "Poka" is a Japanese word meaning inadvertent errors, and "Yokero" is a Japanese word meaning to avoid. Poka Yoke is created to the Japanese quality consultant Shigeo Shingo. PokaYoke is about stopping the process as soon as an error occurs by identifying the error source and seeking to eliminate it.
Poka Yoke is simply a process mechanism designed to prevent a mistake from being made. Well-designed Polka Yoke will eliminate or hugely reduce the opportunity for an error, OR make the error so obvious at the first glance, that the chance of the defect reaching the customer is negligible. Polka Yoke is closely tied to root cause analysis, since it is used to to prevent the causes that give rise to process defects. Polka Yoke methods can include such actions as the creation of a check list, an alteration in the sequence of operation which allows error detection, a computer data entry form that acts as a double check, a message that reminds the user to complete or check a task before allowing them to proceed, a double entry password, and many other possible creative process problem solutions.
There are two main approaches to Polka Yoke correction:
  • Type 1 corrective action, usually believed to be the most effective form of process control, is a type of control which when applied to a process eliminates the possibility of an error condition from occurring.
  • Type 2 corrective action, also known as the detection application method. This is a control that discovers when an error occurs and stops the process flow or shuts down the equipment so that the defect cannot move forward.