Nutritionist evaluation

My daughter had her six year check up today. Everything is good except her weight (she has always been on the smaller side though.) She had her last appointment back in September for a weight check which she hasnt gained any weight since (she did grow 3 inches though.) Her doctor wants her to get blood work done and a CHOP nutrition evaluation. Her doctor said she is probably being overly cautious but she wants to

make sure she doesnt miss anything. What does this type of evaluation entail?