Significance of Mild MCHC Decrease
A mildly decreased MCHC of 31.1 g/dL (just below the reference range of 31.5-35.7 g/dL) in an otherwise normal CBC most likely represents early iron deficiency anemia and requires iron studies (serum ferritin, transferrin saturation, and C-reactive protein) to confirm the diagnosis. 1
Primary Diagnostic Consideration
Low MCHC specifically reflects hypochromic red blood cells with decreased hemoglobin content per unit volume, indicating severe iron restriction during red blood cell production. 1, 2 In your case, the MCHC is only marginally decreased with normal hemoglobin (14.4 g/dL), normal MCV (94 fL), and normal RDW (14.1%), suggesting very early or mild iron deficiency that has not yet progressed to frank anemia.
Essential Workup Required
The minimum evaluation must include: 1
- Serum ferritin (diagnostic if <12 μg/dL; values >100 μg/dL exclude iron deficiency) 1
- Transferrin saturation (<30% supports iron deficiency) 1
- C-reactive protein (to identify inflammatory conditions that may falsely elevate ferritin) 1
Critical Clinical Context
When to Pursue Gastrointestinal Investigation
In adult men and post-menopausal women with confirmed iron deficiency, both upper endoscopy (with small bowel biopsy) and colonoscopy are mandatory to exclude gastrointestinal malignancy, even without overt bleeding. 1 This applies regardless of anemia severity—mild anemia is equally indicative of important disease as severe anemia. 1
For pre-menopausal women, menstrual blood loss is the most common etiology, but gastrointestinal evaluation should still be considered if iron studies confirm deficiency and menstrual losses seem inadequate to explain the findings. 1
Differential Diagnosis to Consider
Thalassemia Minor
- Produces low MCHC but distinguished by normal or low RDW (<14.0%) and elevated red cell count 1, 2
- Your RDW of 14.1% is at the upper limit of normal, making thalassemia less likely but not excluded 1
- Requires hemoglobin electrophoresis for definitive diagnosis before presuming ethnicity-related hemoglobinopathy 1
Chronic Inflammatory Conditions
- Less commonly cause low MCHC than iron deficiency 1, 2
- C-reactive protein measurement identifies inflammatory contribution 1
- Ferritin acts as an acute-phase reactant and may be falsely elevated despite true iron deficiency 1
Technical/Spurious Causes
- Cold agglutinins or lipemia can cause false MCHC elevation or depression 3
- Cell deformability issues may affect automated measurements 4, 5
- Given your only marginally low MCHC with otherwise normal indices, repeat testing may be warranted if initial iron studies are normal 3
Critical Pitfalls to Avoid
Do not attribute low MCHC to dietary insufficiency or menstruation without excluding gastrointestinal malignancy in adult men and post-menopausal women. 1 The American College of Gastroenterology emphasizes that even mild abnormalities require thorough investigation in appropriate populations. 1
Do not assume combined deficiencies are absent—iron plus folate or B12 deficiency may mask microcytosis while showing elevated RDW. 1 Your normal MCV with borderline high RDW (14.1%) could suggest this pattern.
Algorithmic Approach
- Obtain iron studies immediately (ferritin, transferrin saturation, CRP) 1
- If ferritin <12 μg/dL or transferrin saturation <30%: Confirm iron deficiency 1
- If ferritin >100 μg/dL: Iron deficiency excluded; consider thalassemia screening (hemoglobin electrophoresis) or repeat CBC to exclude spurious result 1, 3
- If ferritin 12-100 μg/dL with elevated CRP: Possible iron deficiency masked by inflammation; consider additional testing 1
Prognosis
Treatment of the underlying cause cures the anemia when identified. 1 Even when no cause is detected after thorough investigation, long-term outlook remains good. 1