Evaluation of analytical quality performance through the application of Sigma metrics in the area of clinical hematology: A study at the Clinical Pathology Technical Unit of the Carlos Andrade Marín Specialties Hospital (HECAM)

Abstract

INTRODUCTION: Clinical laboratories seek to standardize processes that guarantee accurate
and reliable results. The Sigma metric has established itself as an effective tool for evaluating analytical performance by identifying defects that traditional quality control methods fail
to detect. A Sigma value ≥6 is considered world-class performance; however, its application in
hematology is still limited.

OBJECTIVES: To evaluate the analytical performance of hematological parameters using the
Sigma metric in Mindray® CAL 6000 and BC 6200 analyzers, in order to identify opportunities
for improvement and optimize the frequency of quality control. 

MATERIALS AND METHODS: A retrospective (cross-sectional) observational study was conducted
using internal quality control (IQC) data recorded between July and December 2024
on Mindray›s Innolab HCP platform. The Sigma calculation was performed using the formula: Sigma = (ETa% value - Bias%)/CV%, taking the total allowable error (ETa) limits from the CLIA guide. The bias and coefficient of variation were calculated.

RESULTS: The parameters white blood cells (WBC), hemoglobin (HGB), and platelets (PLT)
achieved a Sigma ≥6, reflecting world-class performance. Red blood cells (RBC) obtained a Sigma ≥5, considered good, with a need for adjustment, while hematocrit (HCT) showed a Sigma
≥3, corresponding to marginal performance.

CONCLUSIONS: Parameters such as hemoglobin, leukocytes, and platelets showed high
performance, while hematocrit and erythrocytes revealed correctable random and systematic
errors. These results justify adjusting the frequency of quality control according to the Sigma obtained,
improving efficiency, reducing costs, and promoting evidence-based decisions through
integration with models such as the Deming cycle.