Investigation of Creatinine Analysis Deviations

Root Cause Analysis Using Six Sigma DMAIC Methodology

1. DEFINE

Situation & Task

During urine creatinine analysis, significant and unreasonable deviations were observed in standard samples (Control Sample OOC), undermining overall data credibility.

Goals

  • Identify the root cause of the OOC deviation.
  • Restore measurement results to an acceptable range.
  • Ensure experimental legitimacy and compliance.

2. MEASURE

Monitoring Actions

  • Reviewed experimental records for procedural deviations.
  • Checked reagent preparation to rule out contamination.
  • Monitored lab temperature, humidity, and refrigerator temperature.

Measurements

Evaluated data logs to determine if systematic deviations occurred simultaneously with control sample OOC events.

3. ANALYZE

Analysis Methodology

Assessed factors including reagent prep, handling, and environmental effects. Conducted root cause analysis using 5 Whys.

Technical Discovery

UV-Vis results confirmed inconsistent reaction kinetics between the Control Sample and Patient Sample when reacting with Picrate.

Root Cause: The reaction speed is highly temperature-dependent. Patient samples were stored at room temperature, while control samples were taken directly from the refrigerator. This thermal difference caused the control sample to react at a different rate, making it an invalid standard for assessing patient samples.

4. IMPROVE

Corrective Actions

  • Updated SOP to ensure mandatory temperature equilibration of control samples before analysis.
  • Trained lab personnel to follow revised equilibration protocols consistently.

Improvement Result

Measurement values successfully returned to the normal/expected range, restoring data integrity.

Result: Standardized initial reaction temperatures across all sample types.

5. CONTROL

Sustainability

  • Formalized the improved SOP as the routine protocol for future experiments.
  • Established periodic monitoring of lab temperature and measurement consistency logs.

Outcome

Maintained accurate and reproducible results. Provided a reliable operational reference for all ongoing and future laboratory analyses.