Diagnosis of scalp problems begins with a history and physical exam. This may be all that is needed to make the diagnosis. In other cases, further testing is needed. A complete blood count, or CBC, can help detect an infection or blood cancer. A chest x-ray can help diagnose some infections and cancers. In some cases, a biopsy of the skin may be needed. A piece of skin from the scalp is sent to the lab for testing and examination.