This card is not wrong, but an Amboss Q expanded on this in a way that should be reflected in the card (in my opinion!)
Amboss Question:
A 3-year-old boy is brought to the physician by his parents because of a 6-month history of worsening mobility issues. During this period, his parents noticed that he had occasional falls and increasing difficulties climbing stairs and running. The boy had a normal development up until then; he was able to walk by the age of 15 months. There is no personal or family history of serious illness. He takes no medications and immunizations are up-to-date. He is at the 10th percentile for height and 25th percentile for weight. Vital signs are within normal limits. Musculoskeletal examination shows enlarged calf muscles bilaterally. Deep tendon reflexes are 1+ on the lower extremities and 2+ on the upper extremities. He has a waddling gait and when asked to get up from the floor, he supports himself with his hands on his legs to get to an upright position. Which of the following is the most appropriate initial step in diagnosis?
Answer was CK, and genetic studies was wrong, because:
"serum CK concentration should be obtained as the first step in diagnosis and genetic analysis for DMD gene mutations should then be performed to confirm the diagnosis. If the CK level is normal or only mildly increased at the time of symptom onset, DMD is unlikely and a different condition (e.g., spinal muscular atrophy) should be considered."
NOTE: my source for the CK levels blurb in 'extra' is directly from the Amboss question.
