Determining urinary calcium/creatinine cut-offs for the paediatric population using published data

Area of Science:

• Pediatric Nephrology
• Clinical Chemistry
• Biomarker Discovery

Background:

• Establishing abnormal cut-offs for spot urine calcium-to-creatinine ratio (Ca/Cr) in children is crucial but lacks well-defined reference values.
• Existing literature contains numerous reports of urine Ca/Cr excretion, offering a basis for analysis rather than new primary studies.

Purpose of the Study:

• To determine reliable cut-off values for abnormal spot urine Ca/Cr in the pediatric age group (0-18 years).
• To synthesize existing published data to establish laboratory reference ranges for urine Ca/Cr.

Main Methods:

• A systematic review and meta-analysis of 14 published studies reporting urine Ca/Cr ratios in children.
• Data from reviewed studies were plotted to determine a line of best fit (y=-0.3175 ln(x) +1.46, r²=0.85).
• Age-specific cut-offs were recalculated using the derived function and validated against original and in-house data.

Main Results:

• A regression model was established to correlate urine Ca/Cr (mmol/mmol) with age (years).
• Age-specific cut-offs were derived: <1 year (1.50), 1-<2 years (1.25), 2-<5 years (1.00), 5-<10 years (0.70), and 10-18 years (0.60) in mmol/mmol.
• These derived cut-offs were confirmed through consultation with pediatric nephrologists and comparison with in-house data.

Conclusions:

• Established age-specific spot urine Ca/Cr cut-offs for children from birth to 18 years.
• These reference values provide a standardized method for interpreting urine Ca/Cr results in pediatric populations.