What does it mean if the Microalbumin (MA)/creatinine ratio is unable to be calculated due to one or more parameters being outside the Clinical Reportable Range (CRR)?

Understanding "MA/Creatinine Unable to Calculate" Laboratory Result

What This Result Means

This message indicates that either the microalbumin (MA) level, the urine creatinine level, or both fell outside the measurable range of the laboratory analyzer, preventing calculation of the albumin-to-creatinine ratio (ACR). 1

The Clinical Reportable Range (CRR) represents the upper and lower limits that a laboratory instrument can accurately measure and report. 2

Common Causes of This Result

Extremely High Microalbumin Levels

• Macroalbuminuria (≥300 mg/g creatinine) may exceed the upper detection limit of some point-of-care analyzers, particularly those designed primarily for microalbuminuria screening 3, 2
• Nephrotic-range proteinuria can saturate the albumin measurement capacity 4

Extremely Low or High Urine Creatinine

• Very dilute urine (excessive fluid intake, diabetes insipidus) produces creatinine concentrations below the lower detection limit 5
• Very concentrated urine (dehydration, first morning void in some cases) may exceed upper limits 1
• Low muscle mass (malnutrition, sarcopenia, chronic illness) results in reduced creatinine generation and excretion 5, 6

Technical Collection Issues

• Inadequate urine volume for analysis 2
• Improper specimen handling or storage 1

Immediate Next Steps

Repeat the Test with Proper Collection

• Obtain a first morning void midstream sample, which is the preferred specimen type for albumin-to-creatinine ratio testing 1, 3
• Ensure adequate urine volume (minimum 5-10 mL) 2
• Avoid excessive hydration or dehydration before collection 5

Consider Alternative Testing Methods

• If the repeat test also fails to calculate, request quantitative laboratory measurement of both microalbumin and creatinine separately rather than using point-of-care analyzers 2
• Order a 24-hour urine collection for total protein and creatinine if spot testing repeatedly fails, though this is less convenient 4
• Measure total urine protein-to-creatinine ratio (TPCR) as an alternative, which has a broader reportable range and can predict microalbuminuria presence 7

Assess Serum Parameters Simultaneously

• Measure serum creatinine and calculate estimated GFR (eGFR) using validated equations to assess overall kidney function 1
• Consider cystatin C-based eGFR if low muscle mass is suspected, as this provides more accurate assessment independent of muscle mass 1, 5
• Check serum albumin to evaluate for hypoalbuminemia 5

Clinical Context Considerations

Patient Factors Affecting Interpretation

• Gender: Females have lower urinary creatinine excretion, potentially causing ratio calculation issues at extremes 5
• Body habitus: Very low or very high muscle mass affects creatinine generation 5, 6
• Dietary protein intake: High protein intake increases creatinine excretion; low intake decreases it 5
• Hydration status: Both albumin and creatinine concentrations vary with urine dilution 5

Disease States to Consider

• Advanced chronic kidney disease may present with both very high albuminuria and altered creatinine excretion 1
• Nephrotic syndrome produces massive proteinuria that may exceed measurement capabilities 3
• Severe malnutrition or muscle wasting reduces creatinine generation to unmeasurable levels 5

Common Pitfalls to Avoid

• Do not assume normal kidney function based on inability to calculate the ratio—the result may indicate severe abnormality in either direction 6
• Do not rely solely on serum creatinine to assess kidney function, as significant GFR reduction can occur with normal serum creatinine values, particularly in patients with low muscle mass 6, 8
• Do not use conventional creatinine clearance (without cimetidine) as it is less reliable than eGFR and should be abandoned 8
• Recognize that point-of-care analyzers have different reportable ranges than central laboratory methods, and facilities using different analyzers may require different reference ranges 2

When to Escalate Care

Consider nephrology referral if: 3

• Repeated testing continues to show unmeasurable values
• eGFR is <30 mL/min/1.73 m²
• Rapidly progressive kidney disease is suspected
• Uncertainty exists about the underlying etiology