A nine-year old boy with HbSS disease presents with pain in his right leg. The complete blood count shows: Hb 7.5 g/dl; WBC 25x10 /L; PLT 300x10 /L. The MOST appropriate investigation to aid with his...

A nine-year old boy with HbSS disease presents with pain in his right leg. The complete blood count shows:

Hb 7.5 g/dl; WBC 25x10 /L; PLT 300x10 /L. The MOST appropriate investigation to aid with his diagnosis is:

a. PT / PTT
b. Reticulocyte count
c. ESR
d. ASOT