What is the appropriate management for a 24-year-old female patient with normal CBC, iron, ferritin, and TSH levels, but elevated TIBC, slightly elevated alkaline phosphatase, and mildly elevated creatinine, indicating impaired renal function?

Evaluation of Elevated TIBC with Normal Iron Studies

This 24-year-old female has laboratory findings consistent with iron deficiency despite normal ferritin, and requires further evaluation with a complete iron panel including serum iron and transferrin saturation, along with investigation for underlying causes of iron loss. 1

Understanding the Laboratory Pattern

Iron Status Interpretation

• Elevated TIBC (430 mg/dL) indicates increased production of transferrin to compensate for low iron availability, which is the hallmark of iron deficiency even when other markers appear normal 1
• TIBC increases when serum iron concentration and stored iron are low, reflecting the body's attempt to maximize iron-binding capacity 2
• A complete iron panel must include serum iron, TIBC, transferrin saturation (TSAT), and serum ferritin to properly assess iron status 1

Critical Next Step: Calculate Transferrin Saturation

• TSAT is calculated by dividing serum iron by TIBC and multiplying by 100 1
• TSAT <16% in adults confirms iron deficiency, and TSAT <20% indicates absolute iron deficiency in the general population 2, 1
• You need the actual serum iron value to calculate TSAT and definitively diagnose iron deficiency 1

Additional Laboratory Considerations

The Mildly Elevated Creatinine (1.18 mg/dL)

• This creatinine level suggests possible early chronic kidney disease (CKD Stage 2-3), which requires calculation of estimated glomerular filtration rate using the MDRD formula based on age, gender, race, and serum creatinine 2
• Iron deficiency assessment differs in CKD patients: absolute iron deficiency in CKD is defined as TSAT ≤20% with ferritin ≤100 μg/L in predialysis patients 2
• The elevated TIBC pattern can occur in CKD patients with functional iron deficiency, where iron stores exist but cannot be mobilized effectively for erythropoiesis 2

The Low-Normal Alkaline Phosphatase (38 U/L)

• Low alkaline phosphatase can be associated with nutritional deficiencies including zinc and magnesium, which may coexist with iron deficiency 1
• This finding supports the need for comprehensive nutritional assessment

The High-Normal Albumin (5.1 g/dL)

• Elevated albumin suggests possible dehydration or hemoconcentration, which could falsely elevate hemoglobin and mask anemia 2
• Repeat CBC after adequate hydration may reveal underlying anemia

Mandatory Workup

Complete the Iron Panel

• Obtain fasting serum iron to calculate TSAT accurately 3
• Measure serum ferritin if not already done, as ferritin <30 μg/L confirms iron deficiency in non-inflammatory states 1
• Note that ferritin is an acute-phase reactant and can be falsely elevated during inflammation, potentially masking iron deficiency 1
• Consider C-reactive protein to assess for inflammation that might affect ferritin interpretation 1

Identify the Source of Iron Loss

• The presence of iron deficiency mandates a search for the underlying cause, as it rarely occurs without an identifiable source 1
• In a 24-year-old female, assess menstrual blood loss patterns (heavy or prolonged menses) 1, 4
• Evaluate dietary intake for restrictive diets or inadequate iron consumption 1
• Screen for gastrointestinal blood loss with stool guaiac testing, as GI bleeding is a common cause requiring endoscopic evaluation if positive 2, 4
• Consider malabsorption disorders (celiac disease, inflammatory bowel disease) 2
• Assess for NSAID use, blood donation history, or high-impact athletic activity causing hemolysis 1

Common Pitfalls to Avoid

Don't Rely on Ferritin Alone

• Normal ferritin does not exclude iron deficiency, especially if inflammation is present or if the patient has early/functional iron deficiency 2, 1
• Ferritin can remain in the "normal" range while TIBC is already elevated, representing the earliest stage of iron depletion 5

Don't Ignore the Renal Function

• The mildly elevated creatinine requires follow-up with eGFR calculation and urinalysis to assess for proteinuria or hematuria 2
• If CKD is confirmed, iron deficiency management should involve nephrology consultation, as treatment thresholds and approaches differ 2

Timing of Laboratory Tests Matters

• Serum iron has significant diurnal variation (rises in morning, falls at night) and day-to-day variability 3
• For accurate TSAT calculation when screening for iron disorders, obtain fasting morning samples 3
• Avoid testing within 4 weeks of any intravenous iron administration 3

Treatment Considerations (After Diagnosis Confirmed)

• If TSAT <16% and ferritin <30 μg/L confirm absolute iron deficiency, initiate oral iron supplementation (typically 65 mg elemental iron daily) 4, 6
• If CKD is present with eGFR <60 mL/min/1.73m², management should be coordinated with nephrology, as intravenous iron may be preferred over oral supplementation 2
• Address and treat the underlying cause of iron loss concurrently with iron repletion 1, 4