USMLE step 1 : Q 35-37 :Answers

Question Number 35

Correct Answer: B

Explanation:
Chronologic Bias arises in this study since the author is comparing early and delayed repair of Ebstein's anomaly and assigned infants with such anomalies to either early childhood or adult repairs but is ignoring the fact that surgical facilities and resources would have changed substantially in twenty years. The concurrent comparison of control and experimentally treated patients is essential for avoiding chronologic bias. Chronologic bias can occur because diagnostic and therapeutic abilities change over time, and comparisons between control and intervention groups who are treated at different times, perhaps years apart, may reflect differences in an aspect of care other than the effect of the intervention itself. By the time delayed-treatment patients reached adulthood, the differences in outcome of repair might have as much to do with the differences in the diagnostic and surgical techniques of the two time periods as it would with the timing of the operation in the life of the patient.

 

Question Number 36

Correct Answer: B

Explanation:
At two months of age a child no longer clenches its fist tightly. It is able to follows object past the midline. The child smiles socially (after being stroked or talked to) and recognizes its parent. The palmer grasp usually disappears at two months. The Moro's (startle) reflex usually disappears when the child is between three to six months of age.

 

Question Number 37

Correct Answer: B

Explanation:
A three year old can alternate feet when going up steps and learns to pedal a tricycle. She copies a circle, undresses completely and dresses partially and dries hands if reminded. The child typically uses a minimum of 250 words, can use 3-word sentences; uses plurals, past tense; knows all pronouns and understands the concept of 2. The child can also group play, shares toys, takes turns, plays well with others and knows her full name, age and sex. During years three to five a child's vocabulary rapidly increases. A child of this age can distinguish fantasy from reality. The child typically takes risks even though punishment may result from its actions. Imaginary friends are very common at this age