A user's classification of problems identified by proficiency testing surveys.

Area of Science:

• Clinical Laboratory Science
• Quality Assurance in Healthcare
• Medical Diagnostics

Background:

• External proficiency surveys are crucial for laboratory quality assessment.
• Unacceptable results in these surveys can trigger investigations into laboratory performance.
• However, not all flags necessarily point to intrinsic laboratory testing deficiencies.

Purpose of the Study:

• To investigate the root causes of unacceptable results flagged during external proficiency testing.
• To analyze the frequency of different error categories identified in a clinical laboratory setting.
• To improve the interpretation of proficiency testing outcomes.

Main Methods:

• A two-year retrospective analysis of proficiency testing results from three major survey programs (College of American Pathologists, Centers for Disease Control, State of New York).
• Categorization of all encountered "unacceptable" survey flags into predefined causes.
• Quantitative assessment of the prevalence of each identified cause.

Main Results:

• Possible analytic measurement problems accounted for 28% of flags.
• Clerical errors (transcription/forms) were responsible for 16% of flags.
• Inappropriate survey criteria (17%) and specimen issues (11%) were also significant contributors, with 23% having no identifiable cause.

Conclusions:

• External proficiency testing flags require thorough investigation beyond assuming laboratory error.
• A significant proportion of flags result from factors external to the core analytic process, such as clerical or survey-related issues.
• Understanding these diverse causes is essential for accurate quality assessment and targeted improvement strategies in laboratory medicine.