a hemat question--UW's mistake? - homie

[ArchivalUser]

a father brings his son to hospital b/c he noticed his son's eye "getting a little yellow".

CBC:
WBC: 10,000
RBC: 3.5
Hb: 10 g
HCT: 28%
platelet: 240,000
reticulocyte count: 4%

blood smear:
anisocytosis, spherocytosis, polychromatophilia
MCV: 90
MCHC: 38%
MCH:28
total bilirubin: 3.0
direct bilirubin: 0.2

what is the next best step:
a. BM biopsy
b. osmotic fragility test
c. sugar water test
d. hemoglobin electrophoresis
e. serum vit B12 test

UW's anw is b. I know that's what you want to choose when you see spherocytosis. However, in this case the corrected reticulocyte count is <3% (28/45 x 4%), and when you see polychromatia you have to further divide corrected reticulocyte count by 2, so the corrected reticulocyte in this case is very low (close to 1), to me, that's bone marrow suppression, and the 1st thing I do will be bone marrow biopsy. Although the clinical scenario is a hemolytic anemia differential.

Now can anyone plz clarify that with spherocytosis you can still get corrected reticulocyte count lower than 3%? thanks

[ArchivalUser]

spherocytosis is the only condition that would present w/ a High MCHC (nl is 31-36)

[ArchivalUser]

that's true the inc MCHC only seen spherocytosis, but how to explain the extreme low corrected reticulocyte count? or it just that UW guys forgot to consider to correct the reticulocyte count? b/c in UW's explanation, it says: "consider pt's reticulocyte count 4% is high....." oh, well, I guess this is just a bad question, I hope they will correct that soon.