Clinical Significance of Normal Laboratory Values
These laboratory values (creatinine 0.45 mg/dL, CO2 27 mmol/L, ALT 9 U/L, anion gap 8 mmol/L) are all within normal ranges and indicate normal kidney function, normal acid-base status, normal liver function, and normal electrolyte balance.
Kidney Function Assessment
- The creatinine of 0.45 mg/dL indicates normal to high kidney function, falling within the normal range for females (0.43-0.88 mg/dL for Asian females, 0.50-1.10 mg/dL for White females) 1
- This creatinine level corresponds to a GFR ≥90 ml/min per 1.73 m², classified as G1 (normal to increased GFR) according to KDIGO guidelines 1
- Serum creatinine alone should not be used to assess kidney function; GFR estimation using prediction equations (MDRD or Cockcroft-Gault) provides more accurate assessment 1
- A creatinine of 0.45 mg/dL is particularly common in individuals with lower muscle mass, females, or elderly patients, and does not indicate kidney disease 1
Acid-Base and Electrolyte Status
- The CO2 of 27 mmol/L (bicarbonate) is normal, indicating no metabolic acidosis or alkalosis 1
- The anion gap of 8 mmol/L is within the normal reference interval of 10-18 mmol/L (or slightly below), which is acceptable and indicates no accumulation of unmeasured anions 2
- An anion gap of 8 mmol/L with normal bicarbonate excludes high anion gap metabolic acidosis, which would typically present with anion gap >18 mmol/L and low bicarbonate 2
- In chronic kidney disease, anion gap may be normal or only minimally increased despite renal dysfunction, but this patient's normal creatinine excludes significant renal impairment 3, 4
Liver Function Assessment
- ALT of 9 U/L is well within normal range (19-25 U/L for women, 29-33 U/L for men), indicating no hepatocellular injury 5
- ALT is the most specific marker for liver injury due to its high concentration in liver tissue and minimal presence in other organs 5
- This normal ALT excludes significant liver disease including viral hepatitis, nonalcoholic fatty liver disease, alcoholic liver disease, and medication-induced liver injury 5
Clinical Implications
- No further evaluation is needed for these normal laboratory values unless clinical symptoms suggest otherwise 1
- These values indicate preserved organ function across kidney, liver, and acid-base regulatory systems 1, 5
- The combination of normal creatinine, normal bicarbonate, normal anion gap, and normal ALT provides reassurance of normal metabolic homeostasis 1, 2
Important Considerations
- Laboratory reference ranges vary by sex, age, race, and testing facility, so interpretation should account for patient-specific factors 1
- A single set of normal values does not exclude chronic disease if clinical suspicion exists; serial monitoring may be warranted based on symptoms 1
- Normal laboratory values in the context of acute illness may still require clinical correlation, as some conditions present with initially normal labs 1