Should the patient's high‑altitude residence be considered when interpreting his hemoglobin level given his low ferritin and low serum iron?

High-Altitude Residence Must Be Considered When Interpreting Hemoglobin Values

Yes, the patient's high-altitude residence is critically important for accurate interpretation of hemoglobin results, as failure to adjust for altitude will lead to underdiagnosis of true iron deficiency anemia despite low ferritin and serum iron levels. 1

Physiological Basis for Altitude Adjustment

• Long-term residency at high altitude (≥3,000 feet) causes a generalized upward shift in hemoglobin concentration and hematocrit that must be accounted for when screening for anemia 1
• The effectiveness of anemia screening is significantly lowered if cutoff values are not adjusted for altitude, as the positive predictive value becomes non-comparable between sea-level and high-altitude residents 1
• At the patient's altitude, hemoglobin concentration increases by approximately 0.9 g/dL for each 1000 meters of elevation above sea level 2

Specific Adjustment Required

• For a location at high altitude (≥3,000 feet), the normal hemoglobin threshold defining anemia should be increased by approximately 0.5-0.9 g/dL depending on the exact elevation 2
• At 1500 meters altitude, the expected increase is +0.5 g/dL, and at 2000 meters is +0.8 g/dL 2
• The altitude-related increase in hemoglobin is approximately +12% in males at similar elevations 2

Critical Clinical Implications for This Patient

• Despite the physiological elevation in hemoglobin at altitude, this patient has LOW ferritin and LOW serum iron, indicating true iron deficiency that requires treatment 1
• The combination of low iron stores (ferritin) and low available iron (serum iron) represents absolute iron deficiency, regardless of the actual hemoglobin value 1
• If the hemoglobin appears "normal" for sea level but the patient resides at high altitude, this actually represents relative anemia when altitude-adjusted norms are applied 1, 2

Diagnostic Approach

• Measure serum ferritin and transferrin saturation as the primary iron status indicators, as these are less affected by altitude than hemoglobin alone 1
• Ferritin levels <25 ng/mL in males and <11 ng/mL in females indicate insufficient iron stores for effective erythropoiesis, regardless of altitude 1
• Transferrin saturation <20% suggests inadequate iron availability for hemoglobin synthesis and warrants iron supplementation 1
• The presence of iron deficiency requires investigation for blood loss, including stool guaiac testing for gastrointestinal bleeding 1

Common Pitfall to Avoid

• Do not dismiss iron deficiency simply because hemoglobin appears "adequate" by sea-level standards 1, 2
• Failure to account for altitude-related increases leads to underdiagnosis of anemia and delays appropriate iron replacement therapy 2
• Iron deficiency must be corrected before accurately interpreting whether hemoglobin levels are appropriate for the altitude of residence 2

Treatment Decision

• Iron supplementation is indicated when ferritin is low and serum iron is low, regardless of the absolute hemoglobin value 1
• The medical decision regarding iron therapy should be guided by iron status tests (ferritin and transferrin saturation) together with altitude-adjusted hemoglobin levels 1
• In patients with confirmed iron deficiency at high altitude, expect hemoglobin to increase by 4-10 g/L following iron supplementation 1