Preguntas de práctica USMLE Step 2 CK
Las preguntas del test siguen en inglés.
Esta es una muestra gratis de 15 preguntas clínicas al estilo del USMLE Step 2 CK, escrita por el equipo de StudyPDF. Cubre medicina interna, cirugía, pediatría, obstetricia y ginecología, psiquiatría, cribado y prevención, ética y seguridad del paciente, y la bioestadística que usas a pie de cama, y mezcla opción múltiple, marcar todas las que correspondan y completar huecos. Responde las 15 preguntas, después mira tu puntuación y lee la explicación de cada una.
A 72-year-old man reports two episodes of syncope while climbing stairs. Examination shows a crescendo-decrescendo systolic murmur at the right upper sternal border that radiates to both carotids, and the carotid upstroke is slow and low in volume. Which diagnosis best explains these findings?
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Las 15 preguntas de un vistazo
¿Prefieres leer antes de jugar? Abajo están todas las preguntas de la muestra. Las respuestas y explicaciones quedan plegadas hasta que las abras.
1. A 72-year-old man reports two episodes of syncope while climbing stairs. Examination shows a crescendo-decrescendo systolic murmur at the right upper sternal border that radiates to both carotids, and the carotid upstroke is slow and low in volume. Which diagnosis best explains these findings?
- A. Mitral regurgitation
- B. Hypertrophic cardiomyopathy
- C. Aortic regurgitation
- D. Aortic stenosis
Ver respuesta y explicación
Respuesta: D. Aortic stenosis
A slow, low volume carotid upstroke with a systolic ejection murmur radiating to the carotids points to a fixed obstruction at the aortic valve, and exertional syncope means the stenosis is severe enough that cardiac output cannot rise with demand. Mitral regurgitation gives a holosystolic murmur at the apex that radiates to the axilla, and aortic regurgitation is diastolic with a bounding rather than a weak pulse. Hypertrophic cardiomyopathy can sound similar, but its murmur gets louder with Valsalva while the aortic stenosis murmur softens, because less preload means less flow across a fixed valve.
2. A test with a sensitivity of 95 percent and a specificity of 70 percent was validated in a referral clinic. It is now used to screen a general population where the disease is far less common. Which value falls the most in the new setting?
- A. Sensitivity
- B. Specificity
- C. Positive predictive value
- D. Negative predictive value
Ver respuesta y explicación
Respuesta: C. Positive predictive value
Sensitivity and specificity describe how the test behaves in people who do and do not have the disease, so they do not move when prevalence changes. Predictive values do. When prevalence drops, most positives are now false positives, so positive predictive value falls while negative predictive value rises. This is why a test that looks convincing in a specialty clinic can generate mostly false alarms when it is turned into a population screen.
3. Complete the sentence.
In a trial, the event rate is 20 percent in the control group and 15 percent in the treatment group. The absolute risk reduction is 5 percent, so the number needed to treat is _____.
Opciones para el hueco 1: 4, 5, 20, 100
Ver respuesta y explicación
Respuesta: 20
Number needed to treat is 1 divided by the absolute risk reduction, so 1 divided by 0.05 gives 20. Relative risk reduction for the same numbers is 25 percent, which sounds far more impressive from the same data, and that gap is exactly why trials are often reported in relative terms. Always convert to absolute risk reduction before you judge how much a treatment actually buys.
4. Screening recommendations usually specify an age to stop as well as an age to start. What is the main reason for the upper age limit?
- A. Older adults cannot tolerate the screening test
- B. Disease incidence falls sharply with age
- C. Insurance stops covering the test
- D. The benefit of screening appears only after years, so a person with limited life expectancy takes on the harms without living long enough to gain
Ver respuesta y explicación
Respuesta: D. The benefit of screening appears only after years, so a person with limited life expectancy takes on the harms without living long enough to gain
Screening harms are immediate: false positives, biopsies, overdiagnosis and the treatment that follows it. The benefit, fewer deaths from the disease, arrives years later. When remaining life expectancy is shorter than that lag, the arithmetic turns negative. Incidence of most screened cancers actually rises with age rather than falling, which is why the stopping rule is about life expectancy and comorbidity, not about age alone.
5. Which feature best distinguishes preeclampsia from chronic hypertension in a pregnant patient?
- A. Blood pressure elevation documented before 20 weeks of gestation
- B. A family history of hypertension
- C. New onset hypertension after 20 weeks of gestation
- D. Hypertension that persists more than 12 weeks after delivery
Ver respuesta y explicación
Respuesta: C. New onset hypertension after 20 weeks of gestation
The dividing line is timing. Hypertension present before 20 weeks, or still present more than 12 weeks after delivery, is chronic hypertension. New hypertension after 20 weeks with proteinuria or with end organ dysfunction such as thrombocytopenia, elevated transaminases, renal impairment, pulmonary edema or new neurologic symptoms is preeclampsia. The two can coexist, which is called preeclampsia superimposed on chronic hypertension, and that combination raises risk more than either alone.
6. Which findings belong to the diagnostic picture of a manic episode?
Marca todas las que correspondan.
- A. A decreased need for sleep with normal or high energy the next day
- B. Flight of ideas or racing thoughts
- C. Psychomotor retardation with hypersomnia
- D. An increase in goal directed activity or agitation
- E. Anhedonia present nearly every day for two weeks
Ver respuesta y explicación
Respuesta: A. A decreased need for sleep with normal or high energy the next day, B. Flight of ideas or racing thoughts, D. An increase in goal directed activity or agitation
A manic episode needs a distinct period of elevated, expansive or irritable mood together with increased activity or energy, plus symptoms such as decreased need for sleep, racing thoughts, distractibility, inflated self esteem, pressured speech or risky goal directed behavior. Decreased need for sleep is not the same as insomnia: the patient sleeps little and still feels fine. Psychomotor retardation with hypersomnia and two weeks of anhedonia describe a major depressive episode, which is the other pole and not part of mania.
7. A 9-month-old has sudden episodes of crying while drawing his knees up, alternating with periods of lethargy. Examination reveals a sausage shaped mass in the right abdomen and a stool sample mixed with blood and mucus. Which is the most appropriate next diagnostic step?
- A. Abdominal ultrasound
- B. Upper gastrointestinal contrast series
- C. CT of the abdomen with contrast
- D. Colonoscopy
Ver respuesta y explicación
Respuesta: A. Abdominal ultrasound
The picture is classic for intussusception, which peaks between about 6 and 36 months. Ultrasound is the first line study because it is fast, needs no radiation and shows the telescoped bowel as a target or donut on cross section. CT would answer the question too but costs radiation in an infant, an upper GI series looks at the wrong segment, and colonoscopy has no diagnostic role here.
8. Complete the sentence.
The Apgar score rates a newborn's color, heart rate, reflex irritability, muscle tone and respiratory effort, and it is assigned at _____ minute and again at _____ minutes after birth.
Opciones para el hueco 1: 1, 2, 5
Opciones para el hueco 2: 3, 5, 10
Ver respuesta y explicación
Respuesta: 1, 5
Five components are each scored 0, 1 or 2, for a total of 0 to 10, at 1 and 5 minutes. If the 5 minute score stays low, scoring is repeated at intervals while the infant is assessed. The score describes the newborn's condition and how it responds over time, and it is not what triggers resuscitation, which begins on clinical assessment without waiting for a number.
9. Three days after an open abdominal operation a patient has distension, nausea and no flatus. Bowel sounds are absent. An abdominal radiograph shows gas distributed evenly through the small bowel and the colon, with no transition point and no distal collapse. Which explanation fits best?
- A. Adhesive small bowel obstruction
- B. Postoperative ileus
- C. Sigmoid volvulus
- D. Perforated viscus
Ver respuesta y explicación
Respuesta: B. Postoperative ileus
The discriminating detail is the pattern of gas. Mechanical obstruction produces dilated bowel proximally, a transition point and a collapsed segment beyond it. Ileus is a failure of coordinated motility along the whole tract, so gas sits everywhere including the colon with no transition. Volvulus gives a characteristic dilated closed loop, and a perforated viscus is suggested by free air under the diaphragm and peritoneal signs, neither of which is described here.
10. Which statements describe requirements for valid informed consent?
Marca todas las que correspondan.
- A. The patient is told the nature and purpose of the proposed intervention
- B. Risks, expected benefits and the reasonable alternatives, including doing nothing, are disclosed
- C. The patient has decision making capacity and the decision is voluntary and free of coercion
- D. Consent is valid only if a family member countersigns the form
- E. A relative may override the refusal of an adult who has capacity
Ver respuesta y explicación
Respuesta: A. The patient is told the nature and purpose of the proposed intervention, B. Risks, expected benefits and the reasonable alternatives, including doing nothing, are disclosed, C. The patient has decision making capacity and the decision is voluntary and free of coercion
Valid consent needs disclosure, capacity, voluntariness and comprehension, and the signed form is only evidence that the conversation happened. Alternatives, including no intervention at all, are part of the disclosure, because a patient cannot weigh an option they were never told about. A competent adult's decision does not require a relative's approval and cannot be overridden by one.
11. An adult patient with full decision making capacity refuses a blood transfusion on religious grounds and states clearly that she understands she may die without it. Which response is most appropriate?
- A. Seek a court order authorizing transfusion
- B. Ask her adult children to consent on her behalf
- C. Confirm that she understands the consequences and alternatives, then respect the refusal
- D. Wait until she loses consciousness and then transfuse
Ver respuesta y explicación
Respuesta: C. Confirm that she understands the consequences and alternatives, then respect the refusal
An adult with capacity may refuse any intervention, including one that is life sustaining, and the reason for the refusal does not have to be one the clinician agrees with. The physician's job is to confirm capacity, make sure the refusal is informed and voluntary, document it, and continue offering the care the patient does accept. Surrogates and courts step in when capacity is absent, not to overrule a capacitated adult, and transfusing after she becomes unconscious would defeat a decision she made while capable.
12. According to Light's criteria, which findings identify a pleural effusion as an exudate?
Marca todas las que correspondan.
- A. A pleural fluid to serum protein ratio above 0.5
- B. A pleural fluid to serum lactate dehydrogenase ratio above 0.6
- C. A pleural fluid lactate dehydrogenase above two thirds of the upper limit of normal for serum
- D. A pleural fluid glucose identical to the serum glucose
- E. An effusion occurring in decompensated heart failure
Ver respuesta y explicación
Respuesta: A. A pleural fluid to serum protein ratio above 0.5, B. A pleural fluid to serum lactate dehydrogenase ratio above 0.6, C. A pleural fluid lactate dehydrogenase above two thirds of the upper limit of normal for serum
Light's criteria need only one of the three to be met for the fluid to count as an exudate, which makes them very sensitive and somewhat prone to labeling a transudate as an exudate. The distinction matters because it splits the differential: exudates come from inflammation, infection or malignancy that leaks protein across the pleura, while transudates come from pressure problems such as heart failure, cirrhosis or nephrotic syndrome. Fluid glucose equal to serum is unremarkable, and heart failure is the classic transudate.
13. Complete the sentence.
A diagnosis of schizophrenia requires continuous signs of the illness for at least _____ months, while a presentation that has lasted between one and six months is called _____.
Opciones para el hueco 1: 1, 3, 6
Opciones para el hueco 2: brief psychotic disorder, schizophreniform disorder, schizoaffective disorder
Ver respuesta y explicación
Respuesta: 6, schizophreniform disorder
The psychotic disorders are separated mainly by duration. Under one month is brief psychotic disorder, one to six months is schizophreniform disorder, and six months or more of continuous signs, counting prodromal and residual periods, is schizophrenia, with at least one month of active symptoms inside that window. Schizoaffective disorder is defined differently: it needs a mood episode plus a period of psychosis lasting two weeks or more without prominent mood symptoms.
14. Which headache history feature most strongly suggests a secondary rather than a primary headache?
- A. A throbbing unilateral headache with photophobia that eases after sleep
- B. Sudden onset pain that reaches maximum intensity within a minute
- C. A bilateral band like pressure that builds through the workday
- D. Pain that improves after caffeine
Ver respuesta y explicación
Respuesta: B. Sudden onset pain that reaches maximum intensity within a minute
A thunderclap headache, one that peaks within about a minute, is the classic red flag for subarachnoid hemorrhage and other vascular causes, and it warrants urgent evaluation rather than symptomatic treatment. Other red flags include a first severe headache after age 50, fever with neck stiffness, focal neurologic deficits, papilledema, pain that worsens with position or Valsalva, and headache in someone who is immunosuppressed or has cancer. The other three options describe familiar primary patterns, migraine and tension type headache.
15. Which set of laboratory findings best fits iron deficiency anemia?
- A. Low mean corpuscular volume, low ferritin, high total iron binding capacity
- B. Low mean corpuscular volume, high ferritin, low total iron binding capacity
- C. High mean corpuscular volume, normal ferritin, normal total iron binding capacity
- D. Normal mean corpuscular volume, low vitamin B12, high methylmalonic acid
Ver respuesta y explicación
Respuesta: A. Low mean corpuscular volume, low ferritin, high total iron binding capacity
In iron deficiency the stores empty first, so ferritin falls, and the liver makes more transferrin to scavenge what iron is left, which raises total iron binding capacity. Red cells made without enough iron end up small, so the mean corpuscular volume drops. Anemia of chronic disease is the trap: it is also microcytic or normocytic, but ferritin is normal or high because it is an acute phase reactant and total iron binding capacity is low. The high volume and the B12 patterns point to macrocytic causes instead.
Qué evalúa el Step 2 CK y por qué ahora pesa más
El Step 2 CK es el examen de conocimiento clínico de la secuencia del United States Medical Licensing Examination, un programa conjunto de la Federation of State Medical Boards y el National Board of Medical Examiners. En enero de 2022 el Step 1 dejó de dar un número de tres cifras y pasó a informar solo apto o no apto. El Step 2 CK no cambió, así que se convirtió en la única puntuación numérica del USMLE que ve la mayoría de programas de residencia. Ese único cambio es la razón de que exista esta página.
El examen es un solo día de bloques de opción múltiple, de varias horas, y se puntúa con un número. El número de preguntas, la estructura de bloques, el tiempo por bloque y la nota mínima de aprobado vigente los fija el programa USMLE y se han ajustado más de una vez, así que lee esos números en usmle.org y en el esquema de contenido vigente en vez de fiarte de un número de un foro.
El contenido es clínico. Medicina interna se lleva la mayor parte, y cirugía, pediatría, obstetricia y ginecología y psiquiatría llenan casi todo lo demás, más el mantenimiento de la salud y el cribado, la seguridad del paciente, la ética y la comunicación, y la bioestadística aplicada. La mayoría de preguntas son casos clínicos que piden un diagnóstico, el siguiente paso diagnóstico, el mecanismo más probable, o cómo debería cambiar un resultado lo que crees.
Cómo usar esta muestra y cómo estudiar el material
Estas 15 preguntas están montadas alrededor del paso de razonamiento, no de la memoria. Preguntan qué hallazgo estrecha el diagnóstico diferencial, qué te aporta la siguiente prueba diagnóstica, qué propiedad de una prueba se mueve cuando se mueve la prevalencia, y cómo un criterio de duración separa dos diagnósticos psiquiátricos. Ese es el hábito que premia el Step 2 CK, porque un caso clínico suele darte datos suficientes para llegar a la respuesta si sabes para qué sirve cada pieza.
Haz las 15 de una sentada y sin apuntes, después lee la explicación de cada pregunta, también de las que acertaste. Acertar por suerte y saber son cosas distintas, y solo la explicación te dice cuál de las dos pasó. Trata una respuesta incorrecta como un tema, no como un dato. Si fallaste la pregunta del líquido pleural y la de la anemia, la lección es que lees las analíticas valor a valor en vez de como un patrón.
Una nota honesta. Esta página es práctica de examen escrita por el equipo de StudyPDF a partir del esquema de contenido publicado del Step 2 CK. No es orientación médica y ninguna de estas preguntas es de examen real. Donde un caso clínico real te pediría elegir un fármaco o una dosis, esta muestra pregunta por el razonamiento.
Cómo StudyPDF crea tests completos con tu material
Quince preguntas te enseñan dónde tienes flojo el razonamiento clínico. Por sí solas no te preparan para un examen de un día entero, y un banco genérico nunca coincide con lo que subraya el shelf que haces el mes que viene ni los apuntes que te dio tu rotación.
StudyPDF va por otro camino y trabaja con tu material. Subes tu libro de repaso del Step 2, tus apuntes de rotación, una presentación de clase o los dosieres en PDF de tu clerkship, y Bo, el agente de estudio, crea tests de práctica completos con esas páginas exactas. Cada pregunta sale de tu material y cada explicación cita de dónde viene la respuesta, así que puedes saltar directo a la página cuando algo parezca raro. Puedes generar tests nuevos tantas veces como quieras, centrarlos en un solo área como la cardiología o la obstetricia, y seguir qué conceptos sigues fallando entre intentos.
No necesitas un documento para empezar. Si no tienes nada que subir, di solo un tema, por ejemplo los trastornos del equilibrio ácido base, el cribado prenatal o la ética de la decisión por representación, y Bo escribe un test de práctica con eso. Empezar es gratis.
Escrito por el equipo de StudyPDF. Actualizado el 2026-08-19.