TheoryUSMLE Step 3 Medical Prep Study Guide
Study for the USMLE Step 3 Medical Prep with exam topics, practice questions, a free PDF, video walkthrough and timed mock exam links.
How to study for USMLE Step 3 Medical Prep
- Read the topic list so you know what the exam is likely to cover.
- Answer the free practice questions and read every explanation.
- Download the PDF for offline review.
- Use timed mock exams when your untimed practice feels comfortable.
Topics to review
- Safe and effective care environment
- Health promotion and maintenance
- Psychosocial and physiological integrity
- Pharmacology, infection control and patient safety
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Q1A 15-month-old boy is brought to the office for a well-child visit. His mother reports that he does not yet speak any words and does not respond when she calls his name. He can pull to stand and cruise along furniture but does not walk independently. Physical examination shows normal growth parameters. He makes limited eye contact and does not wave bye-bye. The physician reviews standardized developmental screening results indicating delays in both language and social domains. Which of the following screening timelines and actions is most appropriate for this patient? Age Screening Type Action if Delay Identified Key Red Flags 9 months General developmental Refer to early intervention (Part C) No babbling, poor social engagement 18 months General + autism-specific Immediate referral to early intervention + audiology No single words, no pointing, no imitation 24 months Autism-specific Immediate referral for autism evaluation No two-word phrases, loss of skills 30 months General developmental Refer to early intervention if not improving Persistent language or motor delays
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✓ Correct answer: Immediate referral to early intervention and audiology evaluation
This 15-month-old has significant red flags: no single words by 15 months (expected by 12 months), limited social engagement, and not responding to name. These findings warrant immediate referral to early intervention (IDEA Part C) and audiology evaluation to rule out hearing loss. Distractor1 delays necessary intervention. Distractor2 is premature for autism-specific screening before 18 months. Distractor3 inappropriately delays action. Distractor4 misses the need for audiology assessment when language delay is present.
Q2A 7-month-old girl is brought to the office for evaluation. Her parents report that she has not yet started babbling and rarely smiles at them. She can sit with support but cannot sit independently. She reaches for toys with a raking grasp. Birth history is unremarkable and she was born at 39 weeks' gestation. Physical examination shows normal growth parameters. She makes inconsistent eye contact and does not turn toward sounds. Hearing screening at birth was normal. Which of the following milestone patterns is most concerning and warrants urgent evaluation?
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✓ Correct answer: Absent babbling and poor social smile at 7 months
Red flags warranting urgent evaluation include no social smile by 2 months and no babbling by 9 months. At 7 months, absent babbling combined with poor social engagement (rarely smiles, inconsistent eye contact) represents significant delay in multiple domains requiring immediate assessment. Distractor1 describes normal development (sitting independently expected 6-9 months). Distractor2 reflects normal fine motor development (raking grasp appropriate for age). Distractor3 is less concerning as independent walking develops 9-15 months. Distractor4 describes normal variation in language timeline.
Q3A 4-year-old boy with acute lymphoblastic leukemia in remission is brought to the office for a well-child visit. His mother reports that he missed multiple vaccinations during chemotherapy treatment, which ended 6 months ago. His current medications include daily mercaptopurine. Laboratory studies show absolute neutrophil count 1800/mm³ and absolute lymphocyte count 1200/mm³. According to his immunization record, he has not received MMR, varicella, or DTaP vaccines since age 12 months. His oncologist confirms he is no longer severely immunocompromised. Which of the following vaccination schedules is most appropriate? Vaccine Type Minimum Age Minimum Interval Contraindication in Immunocompromise MMR Live 12 months 28 days from other live vaccine Severe immunocompromise Varicella Live 12 months 28 days from other live vaccine Severe immunocompromise DTaP Inactivated 6 weeks 4 weeks between doses None IPV Inactivated 6 weeks 4 weeks between doses None
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✓ Correct answer: Administer DTaP today, then MMR and varicella together in 4 weeks
Inactivated vaccines (DTaP) can be given immediately. Live vaccines (MMR, varicella) require waiting at least 3 months after severe immunosuppression ends; at 6 months post-chemotherapy, he is eligible. Live vaccines must be spaced 28 days apart if not given concurrently, so MMR and varicella should be administered together. Distractor1 violates the 28-day spacing rule for sequential live vaccines. Distractor2 incorrectly continues contraindication beyond necessary timeframe. Distractor3 inappropriately delays inactivated vaccine. Distractor4 violates live vaccine spacing requirements.
Q4A 9-month-old boy is brought to the office for evaluation of poor weight gain. His mother reports he has been irritable during feedings and often refuses to eat. Review of his growth chart shows serial measurements as follows: Age Weight Weight Percentile Length Length Percentile 2 months 5.8 kg 75th 58 cm 50th 4 months 6.9 kg 50th 63 cm 50th 6 months 7.2 kg 25th 66 cm 50th 9 months 7.5 kg 5th 69 cm 25th
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✓ Correct answer: Crossing two major percentile lines from 75th to 5th over 7 months
Concerning growth pattern is crossing two major percentile lines (75th to 5th) over a short interval, indicating failure to thrive. Weight deceleration is disproportionate to length, suggesting inadequate caloric intake rather than genetic short stature. This requires comprehensive evaluation including feeding history, psychosocial assessment, and laboratory studies. Distractor1 describes normal proportional growth. Distractor2 represents constitutional growth variant. Distractor3 shows stable percentiles. Distractor4 misinterprets the data pattern.
Q5A 16-year-old girl comes to the office for a routine health maintenance examination. Her mother accompanies her and remains in the room. The patient appears healthy and reports no concerns. After completing the physical examination, the physician asks the mother to step out to speak with the patient privately. Once alone, the patient reports that she has been sexually active with her boyfriend for 3 months and wants to start oral contraceptives. She says her mood has been 'okay' but admits to feeling 'stressed' about school. She denies suicidal thoughts, substance use, or concerns about her relationship. Which of the following is the most appropriate next step?
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✓ Correct answer: Perform confidential screening for depression and risky behaviors, then discuss contraception
Adolescent visits require confidential screening for depression, sexual behavior, and substance use per HEEADSSS assessment guidelines. The patient's request for contraception and report of stress warrant depression screening before prescribing. State laws generally allow minors to consent for reproductive health services. Distractor1 violates confidentiality and adolescent autonomy. Distractor2 misses depression screening opportunity. Distractor3 focuses on less immediate concern. Distractor4 is premature without comprehensive screening and counseling first.
Q6A 20-month-old girl is brought to the office because her parents are concerned about her development. She speaks only 5 single words and does not combine words. She can walk well and run, but she does not yet walk up stairs. She feeds herself with a spoon and drinks from a cup. She points to objects she wants and waves bye-bye. Physical examination shows normal growth parameters and no dysmorphic features. Which of the following is the most appropriate management at this time?
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✓ Correct answer: Refer to early intervention and audiology for language delay evaluation
A 20-month-old should have 10-25 words and be starting to combine two words (expected by 24 months). Isolated language delay with normal social and motor skills still requires early intervention referral (IDEA Part C) and audiology evaluation to rule out hearing loss. Early intervention maximizes outcomes. Distractor1 inappropriately delays intervention beyond critical window. Distractor2 misses the early intervention opportunity. Distractor3 is premature without hearing evaluation. Distractor4 represents watchful waiting when action is indicated.
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