MCV in Hereditary Spherocytosis
In hereditary spherocytosis (HS), the MCV is typically normal to slightly low (normocytic to mildly microcytic), but the key diagnostic feature is that the mean sphered corpuscular volume (MSCV) is significantly lower than the MCV, with a delta (MCV-MSCV) value >9.6 fL being highly specific for HS. 1, 2
Typical MCV Findings
MCV values in HS patients generally range from normal (82-97 fL) to mildly decreased, distinguishing it from the more pronounced microcytosis seen in iron deficiency anemia or thalassemia 3, 4
The MCV alone is not diagnostic, as it can appear normal in many HS cases, which is why additional red cell parameters are essential 1
The Critical MSCV-MCV Relationship
The MSCV (mean sphered corpuscular volume) is always lower than the MCV in hereditary spherocytosis, creating a characteristic delta value that serves as a reliable screening parameter 2, 4
A delta (MCV-MSCV) value >9.6 fL has 100% sensitivity and 90.57% specificity for diagnosing HS, making this the most useful automated parameter for screening 2
In one study, using a delta (MCV-MSCV) >10 fL demonstrated 82.75% sensitivity and 95.9% specificity for HS diagnosis 4
Other Red Cell Parameters
Mean corpuscular hemoglobin concentration (MCHC) is characteristically elevated in HS (often >339-358 g/L), reflecting the spherical shape and reduced surface area-to-volume ratio of the red cells 3
However, MCHC >35 g/dL alone has poor sensitivity (44.82%) for HS diagnosis and should not be used as a standalone screening test 4
Mean reticulocyte volume (MRV) is typically elevated in HS due to active hemolysis and compensatory reticulocytosis 1, 4
Differential Diagnosis Considerations
The combination of normal-to-mildly-low MCV with elevated MCHC and significantly reduced MSCV distinguishes HS from other microcytic anemias 3
In thalassemia, MCV is typically more markedly reduced with normal MCHC and normal RDW, unlike HS 5, 6
In autoimmune hemolytic anemia (AIHA), the delta (MCV-MSCV) values show wider variation, and the direct Coombs test is positive, helping differentiate from HS 2, 4
Practical Diagnostic Algorithm
When evaluating suspected HS, measure MCV, MSCV, MCHC, and calculate delta (MCV-MSCV) 1, 4
If delta (MCV-MSCV) >9.6 fL, proceed with flow cytometric testing (eosin-5'-maleimide binding test) and direct Coombs test to confirm HS and exclude AIHA 2, 4
Using the algorithm of delta (MCV-MSCV) >10 fL and delta (MRV-MSCV) <25 fL provides 68.9% sensitivity and 98.8% specificity for differentiating HS from immune hemolytic anemia 4
Common Pitfalls
Do not rely on MCV alone for HS diagnosis, as it is frequently normal and can lead to missed diagnosis in mild cases 1, 3
Avoid misinterpreting mildly elevated MCHC as laboratory error; in HS, this reflects true cellular changes and should prompt further investigation 3
Remember that mild or atypical HS cases are easily misdiagnosed when only standard CBC parameters are evaluated without MSCV measurement 3