Ordering tests Practice Questions

Question 1

A researcher is trying to determine whether a newly discovered substance X can be useful in promoting wound healing after surgery. She conducts this study by enrolling the next 100 patients that will be undergoing this surgery and separating them into 2 groups. She decides which patient will be in which group by using a random number generator. Subsequently, she prepares 1 set of syringes with the novel substance X and 1 set of syringes with a saline control. Both of these sets of syringes are unlabeled and the substances inside cannot be distinguished. She gives the surgeon performing the surgery 1 of the syringes and does not inform him nor the patient which syringe was used. After the study is complete, she analyzes all the data that was collected and performs statistical analysis. This study most likely provides which level of evidence for use of substance X?

Accepted Answer

Level 1

Answer

Level 3

Answer

Level 4

Answer

Level 5

Answer

Level 2

Question 2

A 26-year-old medical student comes to the physician with a 3-week history of night sweats and myalgias. During this time, he has also had a 3.6-kg (8-lb) weight loss. He returned from a 6-month tropical medicine rotation in Cambodia 1 month ago. A chest x-ray (CXR) shows reticulonodular opacities suggestive of active tuberculosis (TB). The student is curious about his likelihood of having active TB. He reads a study that compares sputum testing results between 2,800 patients with likely active TB on a basis of history, clinical symptoms, and CXR pattern and 2,400 controls. The results are shown:
Sputum testing positive for TB Sputum testing negative for TB Total
Active TB likely on basis of history, clinical symptoms, and CXR pattern 700 2100 2,800
Active TB not likely on basis of history, clinical symptoms, and CXR pattern 300 2100 2,400
Total 1000 4200 5,200
Which of the following values reflects the probability that a patient with a diagnosis of active TB on the basis of history, clinical symptoms, and CXR pattern actually has active TB?

Accepted Answer

0.25

Answer

1.4

Answer

0.50

Answer

0.70

Answer

0.88

Question 3

A 43-year-old woman presents to her primary care physician with complaints of mild shortness of breath and right-sided chest pain for three days. She reports that lately she has had a nagging nonproductive cough and low-grade fevers. On examination, her vital signs are: temperature 99.1 deg F (37.3 deg C), blood pressure is 115/70 mmHg, pulse is 91/min, respirations are 17/min, and oxygen saturation 97% on room air. She is well-appearing, with normal work of breathing, and no leg swelling. She is otherwise healthy, with no prior medical or surgical history, currently taking no medications. The attending has a low suspicion for the most concerning diagnosis and would like to exclude it with a very sensitive though non-specific test. Which of the following should this physician order?

Accepted Answer

Order a D-dimer

Answer

Obtain chest radiograph

Answer

Obtain spiral CT chest with IV contrast

Answer

Order a lower extremity ultrasound

Answer

Obtain ventilation-perfusion scan

Question 4

A 27-year-old man interested in pre-exposure therapy for HIV (PrEP) is being evaluated to qualify for a PrEP study. In order to qualify, patients must be HIV- and hepatitis B- and C-negative. Any other sexually transmitted infections require treatment prior to initiation of PrEP. The medical history is positive for a prior syphilis infection and bipolar affective disorder, for which he takes lithium. On his next visit, the liver and renal enzymes are within normal ranges. HIV and hepatitis B and C tests are negative. Which of the following about the HIV test is true?

Accepted Answer

It is a qualitative test used for screening purposes.

Answer

It is a quantitative test used for screening purposes.

Answer

A secondary reagent is needed to interpret the results.

Answer

A known antigen binds directly to the patient's serum.

Answer

An unknown antigen binds to the known serum.

Question 5

A 27-year-old woman presents with acute abdominal pain in her right upper quadrant. The pain came on suddenly while she was eating dinner. After this pain she began feeling dizzy and came to the emergency department. In the ED, her blood pressure is 75/40 mmHg, pulse is 100/minute, and she is afebrile. On physical exam, she feels too light-headed to ambulate. She demonstrates normal bowel sounds with tenderness upon palpation in the right upper quadrant. The patient is deemed too unstable for imaging. An abdominal radiograph and CT are reviewed from a recent previous visit to the ED for mild abdominal pain, and are shown in Figures A and B, respectively. Which of the following specific additional findings in her history supports the most likely diagnosis?

Accepted Answer

Use of oral contraceptives (OCPs) for birth control

Answer

Symptoms that began after a fatty meal

Answer

A 15 pack/year history of smoking

Answer

A history of Epstein-Barr virus and participation in rugby

Answer

An extensive history of sexually transmitted diseases (STDs) and pelvic inflammatory disease (PID)

Question 6

A 75-year-old man presents to the emergency department for abdominal pain. The patient states the pain started this morning and has been worsening steadily. He decided to come to the emergency department when he began vomiting. The patient has a past medical history of obesity, diabetes, alcohol abuse, and hypertension. His current medications include captopril, insulin, metformin, sodium docusate, and ibuprofen. His temperature is 104.0°F (40°C), blood pressure is 160/97 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. Abdominal exam reveals left lower quadrant tenderness. Cardiac exam reveals a crescendo systolic murmur heard best by the right upper sternal border. Lab values are ordered and return as below.

Hemoglobin: 15 g/dL
Hematocrit: 42%
Leukocyte count: 19,500 cells/mm^3 with normal differential
Platelet count: 226,000/mm^3

Serum:
Na+: 139 mEq/L
Cl-: 101 mEq/L
K+: 4.4 mEq/L
HCO3-: 24 mEq/L
BUN: 22 mg/dL
Glucose: 144 mg/dL
Creatinine: 1.2 mg/dL
Ca2+: 9.8 mg/dL

Which of the following is the most accurate test for this patient's condition?

Accepted Answer

CT scan

Answer

Colonoscopy

Answer

Sigmoidoscopy

Answer

Amylase and lipase levels

Answer

Barium enema

Question 7

A 68-year-old woman presents to the hospital for an elective right hemicolectomy. She is independently mobile and does her own shopping. She has had type 2 diabetes mellitus for 20 years, essential hypertension for 15 years, and angina on exertion for 6 years. She has a 30-pack-year history of smoking. The operation was uncomplicated. On post-op day 5, she becomes confused. She has a temperature of 38.5°C (101.3°F), respiratory rate of 28/min, and oxygen saturation of 92% on 2 L of oxygen. She is tachycardic at 118/min and her blood pressure is 110/65 mm Hg. On chest auscultation, she has coarse crackles in the right lung base. Her surgical wound appears to be healing well, and her abdomen is soft and nontender. Which of the following is the most likely diagnosis?

Accepted Answer

Sepsis

Answer

Malignant hyperthermia

Answer

Drug-induced fever

Answer

Multiple organ dysfunction syndrome

Answer

Non-infectious systemic inflammatory response syndrome (SIRS)

Question 8

A medical research study is beginning to evaluate the positive predictive value of a novel blood test for non-Hodgkin’s lymphoma. The diagnostic arm contains 700 patients with NHL, of which 400 tested positive for the novel blood test. In the control arm, 700 age-matched control patients are enrolled and 0 are found positive for the novel test. What is the PPV of this test?

Accepted Answer

400 / (400 + 0)

Answer

700 / (700 + 300)

Answer

400 / (400 + 300)

Answer

700 / (700 + 0)

Answer

700 / (400 + 400)

Question 9

In a randomized controlled trial studying a new treatment, the primary endpoint (mortality) occurred in 14.4% of the treatment group and 16.7% of the control group. Which of the following represents the number of patients needed to treat to save one life, based on the primary endpoint?

Accepted Answer

1/(0.167 - 0.144)

Answer

1/(0.144 - 0.167)

Answer

1/(0.300 - 0.267)

Answer

1/(0.267 - 0.300)

Answer

1/(0.136 - 0.118)

Ordering tests

Study Resources

Lessons

Questions

Lessons

Initial diagnostic workup approach

History-directed testing

Physical exam-directed testing

Laboratory test selection principles

Imaging study selection principles

Specialized diagnostic procedures

Screening vs diagnostic testing

Cost-effective test ordering

Pre-test probability assessment

Diagnostic algorithms by presentation

Appropriate test sequencing

Managing incidental findings

Avoiding unnecessary testing

Practice Questions

About Ordering tests for USMLE

Lessons in Ordering tests

Master Ordering tests