Assessment of eGFR 89 and Creatinine 1.05 in the Context of Fever
An eGFR of 89 mL/min/1.73 m² and serum creatinine of 1.05 mg/dL fall within the normal to mildly reduced range of kidney function (CKD-EPI Stage G2), but fever can transiently elevate creatinine and affect eGFR calculations, making these values potentially misleading during acute illness. 1
Understanding the Baseline Values
eGFR of 89 mL/min/1.73 m² is classified as Stage G2 (mildly reduced GFR) according to KDIGO staging, which defines this range as 60-89 mL/min/1.73 m² 1
This level is above the threshold of 60 mL/min/1.73 m² that defines clinically significant chronic kidney disease 1
In healthy adults, reference intervals for eGFR using the MDRD equation range from 63.5-124.6 mL/min/1.73 m², meaning an eGFR of 89 falls within the normal range for many individuals 2
Serum creatinine of 1.05 mg/dL is generally within normal limits for most adults, though normal ranges vary by age, sex, and muscle mass 3
Critical Impact of Fever on These Values
Fever is a known confounding factor that can transiently elevate serum creatinine and artificially lower eGFR calculations. 1
The American Diabetes Association explicitly states that fever may elevate urinary albumin-creatinine ratio independently of kidney damage 1
While the guidelines specifically mention fever's effect on albuminuria, the physiologic stress of fever can also affect creatinine generation and renal hemodynamics 1
Exercise within 24 hours, infection, fever, congestive heart failure, marked hyperglycemia, and marked hypertension are all recognized as factors that can alter kidney function parameters independently of true kidney damage 1
Clinical Interpretation Algorithm
Follow this approach to interpret these values correctly:
Do not make definitive conclusions about kidney function during active fever - wait until the fever resolves 1
Repeat measurements 2-4 weeks after fever resolution to obtain accurate baseline kidney function 1
If eGFR remains 60-89 mL/min/1.73 m² after fever resolves, this represents Stage G2 (mildly reduced GFR), which requires:
Check for albuminuria using urine albumin-to-creatinine ratio once fever resolves, as this determines whether Stage G2 eGFR represents true kidney disease 1
Important Caveats About eGFR Accuracy
Several factors limit the reliability of eGFR calculations, particularly in this range:
eGFR has not been validated as accurate in high, low, or rapidly changing GFRs, and the uncertainty at the critical 60 mL/min/1.73 m² threshold is calculated to be ±11 4, 5
Caution is needed when interpreting eGFR between 49-71 mL/min/1.73 m² due to measurement uncertainty 5
eGFR assumes average body size and lean body weight, making it inaccurate in many populations including older adults, obese individuals, and those with unusual muscle mass 4
Serum creatinine reflects not only renal excretion but also creatinine generation, intake, and metabolism, meaning it is an imperfect marker of kidney function 3
Exogenous factors like creatine supplements can artificially elevate serum creatinine and lower calculated eGFR 6
Risk Stratification When Values Normalize
If these values persist after fever resolution:
An eGFR of 89 with normal albuminuria (<30 mg/g) represents low to moderately high risk depending on other factors 1
Stage G2A1 (eGFR 60-89 with normal albuminuria) is classified as moderately high risk (yellow zone) in the KDIGO risk stratification 1
Annual monitoring is appropriate for Stage G2A1, with no need for nephrology referral unless other concerning features develop 1
Nephrology referral is only indicated if eGFR falls below 30 mL/min/1.73 m² or if there are difficult management issues 1
Bottom Line for Clinical Action
During active fever, these values should not be used to diagnose kidney disease or guide clinical decisions. Repeat testing after fever resolution is essential. If values remain stable at eGFR 89 and creatinine 1.05 without fever, and albuminuria is normal, this represents acceptable kidney function that requires only routine annual monitoring. 1