A Reflex Protocol for Creatinine Testing Reduces Costs and Maintains Patient Safety.

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Diagnostic Testing

Background:

• Creatinine measurement commonly uses Jaffe and enzymatic methods.
• The Jaffe method is economical but prone to interferences, prompting calls for its discontinuation.
• Evaluating alternative protocols is crucial for optimizing laboratory diagnostics.

Purpose of the Study:

• To identify the most cost-effective and safe protocol for creatinine measurement.
• To assess the utility of a risk-based reflex testing strategy.

Main Methods:

• A retrospective review of outpatient creatinine measurements was conducted over one year.
• A risk-based reflex protocol was implemented, measuring samples first by the Jaffe method.
• Samples were reflexed to the enzymatic method if estimated glomerular filtration rate (eGFR) was between 55-65 mL/min/1.73 m².

Main Results:

• Out of 104,530 measurements, 10.9% were reflexed to the enzymatic method.
• The Jaffe method exhibited a positive bias; 3.4% of reflexed specimens were discordant.
• False negatives (1.2%) and false positives (29.9%) were observed, with few considered clinically significant.

Conclusions:

• The implemented reflex protocol significantly reduces costs associated with creatinine measurement.
• This protocol offers a safe and cost-effective approach to creatinine testing with acceptable clinical risk.