Gastroenterology Flashcards
1
Q
- A 58-year-old African American man presents
with a 2-month history of burning epigastric pain
and intermittent difficulty swallowing. The pain is
not relieved by positional changes or eating, and
he has tried calcium carbonate (500 mg) chewable
tablets when symptoms occur, resulting in minimal
relief. He takes amlodipine 5 mg/day for hyperten-
sion and ibuprofen for occasional back pain. Which
action is best for this patient?
A. Initiate famotidine 20 mg/day.
B. Refer for possible endoscopic evaluation.
C. Initiate omeprazole 20 mg twice daily.
D. Change amlodipine to hydrochlorothiazide.
A
- Answer: B
This patient has signs of dysphagia, an alarm symptom
that is sometimes associated with a more complicated
case of GERD. The patient has tried antacids with
minimal relief and has a history of NSAID use. The
patient is older than 45 years, which increases his risk
of developing gastric cancer. Therefore, he should be
referred for endoscopic evaluation to rule out a more
complicated disease (Answer B). Using either H2
RAs
(Answer A) or a PPI as initial therapy after endoscopic
evaluation would be appropriate if the patient does
not respond to antacids; however, a twice-daily dos-
ing of PPIs (Answer C) is not necessary as initial dos-
ing. Changing medications that reduce LES tone (e.g.,
calcium channel antagonists) is an appropriate recom-
mendation for reducing GERD symptoms; this should
be considered after invasive testing is performed
(Answer D).
2
Q
- A 50-year-old woman is seen in the clinic for severe
pain related to the swelling of three of her meta-
carpophalangeal joints on each hand and swelling
of her right wrist. She cannot write or perform her
usual household activities. Radiograms of these
joints reveal bony decalcifications and erosions.
A serum rheumatoid factor is obtained, which is
elevated. Her medical history includes type 2 dia-
betes, hypertension, and dyslipidemia. Her med-
ications include metformin 1000 mg twice daily,
glyburide 10 mg/day, metoprolol 100 mg twice
daily, aspirin 81 mg/day, and rosuvastatin 5 mg/
day. The primary care provider would like to ini-
tiate systemic anti-inflammatory therapy for this
patient’s rheumatoid arthritis with high-dose non-
steroidal anti-inflammatory drug (NSAID) ther-
apy; however, the primary care provider is worried
about potential gastrointestinal (GI) toxicity. What
is the best regimen for treating this patient’s pain
while minimizing the risk of GI toxicity?
A. Celecoxib 400 mg twice daily.
B. Indomethacin 75 mg/day plus famotidine 10
mg/day.
C. Naproxen 500 mg twice daily plus omeprazole
20 mg/day.
D. Piroxicam 20 mg/day plus misoprostol 600
mcg three times daily.
A
- Answer: C
For patients beginning long-term NSAID therapy, a
thorough assessment of patient- or drug-related factors
that may predispose them to the development of GI toxic-
ity is necessary. Likewise, an evaluation of the patient’s
level of CV risk is necessary. Given the use of low-dose
aspirin for preventing CV events, this patient would be
considered at high risk of CV events. Efforts to avoid
GI toxicity should include the use of the GI agent that
is least toxic at the lowest effective therapeutic dose. A
GI-protective agent should be considered to minimize
NSAID-induced erosions and ulcers. Indomethacin
(Answer B) and piroxicam (Answer D) are more likely
to cause GI complications than is naproxen (Answer C).
Use of COX-2 inhibitors (Answer A) is acceptable in
patients with rheumatoid arthritis because these agents
reduce GI complications and effectively treat pain.
However, this patient has CV risk factors including dia-
betes, hypertension, and dyslipidemia. Recent findings
of increased CV events, especially with high doses of
COX-2 inhibitors, would preclude their use. Therapy
with an acid-suppressive agent is also an accept-
able choice for GI prevention in users of nonselective
NSAIDs. Proton pump inhibitors are effective for this
indication (Answer C). The H2
RAs are ineffective in
preventing serious NSAID-induced GI complications
(Answer B). Misoprostol, although effective, is associ-
ated with a high incidence of diarrhea and abdominal
pain and the need for multiple daily dosing (Answer D).
Given that this patient is considered at moderate risk of
GI complications, because of the patient’s use of aspirin
and need for high-dose NSAIDs, the use of naproxen
plus a PPI would be preferred, according to the recent
ACG guidelines (Answer C).
3
Q
- A 68-year-old Hispanic man is assessed in the
emergency department for a 36-hour history of
black, tarry stools; dizziness; confusion; and vom-
iting a substance resembling coffee grounds. He
has a medical history of osteoarthritis, hyperten-
sion, myocardial infarction (MI) in 2009 and 2011,
and seasonal allergies. He has taken naproxen 500
mg twice daily for 4 years, metoprolol 100 mg
twice daily, aspirin 325 mg/day, and loratadine
10 mg/day. Nasogastric (NG) aspiration is posi-
tive for blood, and subsequent endoscopy reveals
a 3-cm antral ulcer with a visible vessel. The vessel
is obliterated using an epinephrine solution, and a
rapid urease test is negative for Helicobacter pylori.
Which recommendation is best for this patient?
A. Intravenous famotidine 20 mg twice daily for
5 days.
B. Sucralfate 1 g four times daily by NG tube.
C. Oral lansoprazole 15 mg/day by NG tube.
D. Pantoprazole 80 mg intravenous bolus, fol-
lowed by an 8-mg/hour infusion.
A
- Answer: D
This patient presents with signs and symptoms consis-
tent with an NSAID-induced upper GI bleed. He has
several risk factors for NSAID-induced GI bleeding,
including age older than 60 years, use of aspirin, and
long duration of NSAID use. The presence of under-
lying CV disease, although not a direct risk factor,
may also contribute to increases in NSAID GI toxicity.
He also has many criteria that place him at high risk
of rebleeding. According to the consensus recommen-
dations for nonvariceal bleeding, he should receive an
intravenous PPI by bolus and subsequent continuous
infusion for 72 hours (Answer D). Note that the guide-
lines provided state that this therapeutic approach can
be extrapolated to patients with NSAID-induced ulcers
and bleeding, even though most of the data included in
the guidelines pertain to non–NSAID-induced causes
of upper GI bleeding. He will then require treatment
with an appropriate dose of an oral PPI for at least 8
weeks; after that, he should be assessed for possible
continued prophylactic use. H2RAs (Answer A) are less
efficacious for the treatment and prevention of rebleed-
ing for NSAID-induced ulcers. Sucralfate (Answer B)
has minimal efficacy in the setting of acute GI bleed-
ing. Oral PPIs (Answer C) are effective in preventing
and healing NSAID-induced ulcers; however, in this
case, the lansoprazole dose is inadequate for treatment.
Oral PPIs should be used at an appropriate dose after
intravenous therapy.
4
Q
- A 38-year-old woman presents with an 8-week
history of new-onset cramping abdominal pain
together with 2–4 bloody stools per day. The
patient does not have tachycardia or fever. She has
a medical history of urinary tract infection and
reports an allergy to “sulfa”-containing medica-
tions (shortness of breath). Colonoscopy reveals
diffuse superficial colonic inflammation consis-
tent with ulcerative colitis (UC). The inflammation
is continuous and extends to the hepatic flexure.
Which drug therapy is best?
A. Sulfasalazine extended release tablets 1 g
orally three times daily.
B. Hydrocortisone enema 100 mg every night.
C. Mercaptopurine 75 mg orally once daily.
D. Mesalamine (Delzicol) 800 mg orally three
times daily.
A
- Answer: D
Given this patient’s presenting symptoms, she would be
classified in the mild active disease category. First-line
therapy for active extensive disease would consist of an
oral aminosalicylate at a dose equivalent to mesalamine
at least 2 g/day. A product such as Delzicol (Answer
D) is formulated to release mesalamine in the colon,
which would be appropriate in this case. Sulfasalazine
(Answer A) has reported efficacy for this indication and
is activated in the colon; however, this patient reports a life-threatening allergy to sulfonamide-contain-
ing medications. Topical therapy with hydrocortisone
enema (Answer B) would be appropriate if the patient
had disease distal to the splenic flexure. Immune mod-
ulators such as mercaptopurine (Answer C) have a long
onset of action (3–15 months) and are not appropriate
for acute active disease.
5
Q
- A 45-year-old African American man with a his-
tory of alcoholic cirrhosis (Child-Pugh class B) was
seen in the clinic for a follow-up. He was recently
referred for a screening endoscopy, which revealed
several large esophageal varices. He has no his-
tory of bleeding; 1 month ago, propranolol 10 mg
orally three times daily was initiated. At that time,
his vital signs included body temperature 98.7°F
(37°C), heart rate 85 beats/minute, respiratory rate
15 breaths/minute, and blood pressure 130/80 mm
Hg. At his evaluation today, he seems to be tolerat-
ing the propranolol dose and has no new concerns.
His vital signs now include body temperature
98.6°F, heart rate 79 beats/minute, respiratory rate
14 breaths/minute, and blood pressure 128/78 mm
Hg. What is the best course of action?
A. Continue current therapy, with a close fol-
low-up in 4 weeks.
B. Increase propranolol to 20 mg orally three
times daily.
C. Add isosorbide dinitrate 10 mg orally three
times daily.
D. Change propranolol to atenolol 25 mg orally
once daily.
A
- Answer: B
Primary prophylaxis of bleeding should be instituted in
patients with large varices and cirrhosis. Nonselective
β-blockers are appropriate as first-line therapy. Therapy
should be targeted to achieve a resting heart rate of
55 beats/minute or a 25% reduction from baseline. The
patient has taken propranolol for 1 month and has not
met these goals (Answer A). Because he is tolerating
propranolol, the dose should be increased (Answer B),
and he should be observed to reassess the need for fur-
ther dosage adjustments. Adding a nitrate (Answer C)
would increase the reduction in portal pressures; how-
ever, nitrates have not been shown to improve mor-
tality. Most patients have an increased risk of adverse
effects with this combination. Nonselective β-block-
ers are preferred to cardioselective agents (Answer D)
because antagonism of the β-receptor prevents splanch-
nic vasodilation.
6
Q
- A new stool antigen test to detect H. pylori was
tested in 1000 patients with suspected peptic ulcer
disease (PUD), and 865 had a positive result. All
patients had also undergone a concomitant endos-
copy with biopsy and culture as the gold standard
comparative test, and 900 had a positive result. Of
these 900 patients with confirmed disease, only 850
also had a positive result with the new stool antigen
test. From these results, which best represents the
sensitivity and specificity of the new stool antigen
test?
A. Sensitivity 82%, specificity 86%.
B. Sensitivity 85%, specificity 97%.
C. Sensitivity 94%, specificity 85%.
D. Sensitivity 96%, specificity 90%.
A
- Answer: C
The sensitivity of a test can be thought of as the pro-
portion of patients with a disease who have a positive
test, whereas specificity deals with the proportion of
patients without the disease who have a negative test.
Calculating these values is accomplished by establish-
ing a 2 × 2 table representing the results of the test. The
sensitivity can be calculated by dividing the number of
patients having the disease using the new test who were
also positive using a gold standard test (true positives),
which in this case is 850, by the number of patients
receiving a diagnosis of having the disease using the
gold standard, which in this case is 900. The 900 rep-
resents the true positives and 50 patients with the dis-
ease but without the diagnosis of it, according to the
new test (false negatives). Specificity can be calculated
by taking the number of patients not having the disease
using the gold standard who tested negative with the
new test (true negatives = 85). Next, divide this result
by the number of patients who truly had no disease
using the gold standard, 100, which incorporates the 15
patients who tested positive with the new test but truly had no disease (i.e., false positives). Sensitivity = 850/
(850 + 50) = 94%; specificity = 85/(85 + 15) = 85%.
(Answer C). The other numerical manipulations possi-
ble are not representative of sensitivity and specificity
(Answers A, B, and D).
7
Q
- A 50-year-old Asian woman is seeking advice
regarding a recent possible exposure to hepatitis
A virus (HAV). She saw on the local news report
that a chef at a local restaurant where she had eaten
about 3 weeks earlier had active HAV. Having heard that HAV could be transmitted through food,
she would like to know her options. She has not
previously received the HAV vaccine. Which is the
best recommendation for this patient?
A. Initiate HAV vaccine.
B. Administer HAV immune globulin.
C. Continue to observe the patient for symptoms.
D. Initiate HAV vaccine and immune globulin.
A
- Answer: C
Postexposure therapy for HAV may be offered to
restaurant patrons if a food handler at a restaurant is
documented to have HAV and is considered infectious
while handling food. The most effective therapies
for postexposure prophylaxis are administration of
HAV immune globulin or vaccine. The efficacy of the
vaccine approaches that of immune globulin, but only
in patients younger than 40 years, according to the
Centers for Disease Control and Prevention guidelines.
The period for administration should be within 14 days
of exposure; therefore, this patient does not meet the
criteria for receiving HAV immune globulin (Answer
B) or vaccine (Answer A). She should be observed
for signs and symptoms of active disease (Answer
C). Hepatitis A vaccine should be offered to patients
as preexposure therapy if they are considered at risk
of exposure to HAV. The combination of vaccine and
immune globulin for postexposure therapy is unneces-
sary (Answer D).
8
Q
- A 48-year-old woman is admitted to the general
medicine floor with abdominal pain, severe nau-
sea and vomiting, and abdominal distension sec-
ondary to alcoholic hepatitis. She has a history of
alcohol abuse for 20 years and takes no current
medications. Her serum creatinine (SCr) is 0.5 mg/
dL, aspartate aminotransferase (AST) 250 IU/L,
alanine aminotransferase (ALT) 60 IU/L, total
bilirubin 10.3 mg/dL, prothrombin time 19 sec-
onds (control 12 seconds), and albumin 2.1 g/L.
An abdominal paracentesis shows no evidence
of spontaneous bacterial peritonitis (SBP). She
reports no known drug allergies. What is the treat-
ment for this patient’s alcoholic hepatitis?
A. Naproxen 220 mg orally twice daily.
B. Octreotide 50 mcg/hour intravenously.
C. Prednisolone 40 mg/day.
D. Midodrine 7.5 mg three times daily.
A
- Answer: C
This patient presents with elevated aminotransfer-
ases, consistent with alcoholic hepatitis. Prognosis of
alcoholic hepatitis can be initially evaluated with the
Maddrey discriminant function (MDF) score, cal-
culated as 4.6 × (Patient’s PT − Control PT) + Total
bilirubin (mg/dL), where PT is prothrombin time.
Patients whose score is greater than 32 are believed
to have a poor prognosis. This patient’s MDF score is
42.5; therefore, she would qualify for treatment with
a 4-week course of prednisolone 40 mg/day, followed
by a 2-week taper (Answer C). This can lead to a 30%
decrease in the risk ratio of short-term death. Naproxen
(Answer A), though having anti-inflammatory activity,
has no role in the treatment of alcoholic hepatitis and
may precipitate acute kidney injury in patients with
liver disease; therefore, it should be avoided. Octreotide
(Answer B) would be indicated in the setting of acute variceal bleeding, and midodrine (Answer D) is indi-
cated for hepatorenal syndrome. This patient has no
evidence of either condition.
9
Q
- A 50-year-old man (weight 80 kg) with a history
of intravenous drug abuse and chronic hepatitis C
virus (HCV; genotype 3 with compensated cirrho-
sis and NS5A resistance-associated substitutions
present) started taking sofosbuvir 400 mg/velpa-
tasvir 100 mg daily and ribavirin 600 mg orally
twice daily 2 weeks ago. He returns to the clinic
today with fatigue, scleral icterus, and pallor. There
is no clinical evidence of bleeding. Laboratory val-
ues reveal the following: hematocrit 31% (baseline
39%), total bilirubin 3.2 mg/dL (indirect 2.7 mg/
dL, direct 0.5 mg/dL), AST 150 IU/mL (baseline
300 IU/mL), ALT 180 IU/mL (baseline 400 IU/
mL), SCr 0.7 mg/dL, HCV RNA 1 × 106
IU/mL
(baseline 2.3 × 106
copies/mL), white blood cell
count (WBC) 7.8 × 103
cells/mm3
, and platelet
count 160,000/mm3
. What is the most likely cause
of this patient’s current symptoms?
A. Worsening of his liver disease secondary to
inadequate treatment.
B. An adverse effect secondary to treatment with
sofosbuvir.
C. Systemic manifestations of chronic HCV
disease.
D. An adverse effect secondary to treatment with
ribavirin.
A
- Answer: D
The treatment used in this case for chronic HCV,
genotype 3 with compensated cirrhosis and NS5A
resistance-associated substitutions is the fixed-dose
combination of sofosbuvir 400 mg/velpatasvir 100 mg
with the addition of ribavirin. Alternatively, sofosbuvir/
velpatasvir/voxilaprevir may be considered. Genotype
2 responds well to therapy. Although this patient
appears to be responding to treatment, as indicated by
reductions in aminotransferases and HCV RNA, the
earliest that HCV RNA should be evaluated is 4 weeks,
not 2 weeks (Answer A). This patient does not appear
to have adverse effects to sofosbuvir (Answer B) or
symptoms consistent with extrahepatic manifestations
of HCV (e.g., glomerulonephritis or rheumatologic dis-
orders; Answer C). The patient does have evidence of
hemolysis, including scleral icterus, rapid decline in
hematocrit, fatigue, and elevated indirect bilirubin,
probably representing hemolytic anemia secondary to
ribavirin, which commonly occurs within the first 2
weeks of therapy (Answer D). Furthermore, there is no
evidence that the decrease in hematocrit is secondary
to bleeding.
10
Q
- A 35-year-old man with a history of Crohn disease
(CD) is in the clinic today with a chief concern
of mucopurulent drainage from an erythema-
tous region on his abdomen. Examination reveals
a moderate-size enterocutaneous fistula in the
left upper abdominal area. He takes mesalamine
(Pentasa) 250 mg in four capsules three times daily
and azathioprine 150 mg/day. His physician wants
to prescribe infliximab. Which recommendation is
best when initiating infliximab therapy?
A. Rule out tuberculosis by purified protein
derivative or QuantiFERON-TB test.
B. Administer a test dose before the initial
infusion.
C. Admit the patient to the hospital for the admin-
istration of all doses.
D. Obtain an echocardiogram to assess cardiac
function.
A
- Answer: A
Infliximab is an appropriate agent for the treatment of
fistulizing CD. Because of its effects on TNF, latent
infections such as tuberculosis can become reactivated
during therapy. Therefore, patients should have a puri-
fied protein derivative or QuantiFERON-TB test to rule
out underlying tubercular disease before treatment is
initiated (Answer A). Although infliximab therapy is
associated with infusion-related reactions, administer-
ing a test dose is not routinely recommended (Answer
B). Infliximab may be administered in a clinic setting; it
does not require admission to the hospital for monitor-
ing (Answer C). Infliximab therapy is associated with
exacerbations of underlying heart failure and is contra-
indicated in patients with New York Heart Association
class III or IV disease. This patient is young, with no
history of heart failure and no clinical signs of heart
failure. Therefore, a baseline echocardiogram is not
necessary to assess cardiac function (Answer D).
11
Q
- A 41-year-old woman (height 65 inches, weight 70
kg) with a history of bipolar disorder and recurrent
urinary tract infections is admitted to the general
medicine service with severe nausea, vomiting,
fever, and back pain. On examination, she has
fever, dry mucous membranes, and right-sided cos-
tovertebral tenderness. A urinalysis, which reveals
many bacteria, is positive for leukocyte esterase.
Her SCr is 1.3 mg/dL, and blood urea nitrogen
(BUN) is 29 mg/dL. She takes risperidone 6 mg
twice daily and sertraline 150 mg/day. She reports
an allergy to trimethoprim/sulfamethoxazole that
causes a rash. Which drug would be best for treat-
ing this patient’s nausea?
A. Prochlorperazine 10-mg tablet orally twice
daily.
B. Metoclopramide orally disintegrating tablets
(ODTs) 5 mg three times daily.
C. Ondansetron 4 mg intravenously three or four
times daily.
D. Diphenhydramine 50 mg intravenously three
or four times daily.
A
- Answer: C
Treatment of nausea and vomiting in medical inpatients
can be accomplished by administering a variety of anti-
emetics. Nausea and vomiting are common symptoms
associated with pyelonephritis, and they will subside
once appropriate antibiotic therapy adequately treats
the infection. However, patients will need symptomatic
relief until the antibiotics take effect. Agents typically
used for medical inpatients include phenothiazines
and serotonin antagonists. The use of intravenous or
rectal formulations is usually preferred for patients
with severe nausea, such as this patient. Ondansetron
(Answer C) is a serotonin antagonist that can be admin-
istered as needed intravenously and is effective in treat-
ing nausea caused by a variety of medical conditions.
Despite its effects on serotonin, it should not cause any
significant interaction with the patient’s sertraline dose.
Prochlorperazine (Answer A), a commonly used anti-
emetic, would be a viable option; however, using the oral
product in this case would not be preferred, given that
the patient has severe vomiting. In addition, prochlor-
perazine is a dopamine antagonist, and the patient is
receiving a high dose of risperidone. This combina-
tion can lead to the development of EPS and, in severe
cases, QTc prolongation. Metoclopramide (Answer B)
is typically used as an antiemetic when gastroparesis is
present or as an adjunctive therapy for patients whose
other therapies have failed. Metoclopramide also has
dopamine antagonist effects that can lead to the devel-
opment of EPS. Diphenhydramine (Answer D) is more
effective for nausea related to motion sickness, but it
would not effectively treat severe short-term nausea or
the other options.
12
Q
- A 75-year-old man (height 58 inches, weight 68 kg)
with a history of hypertension, type 2 diabetes, and
chronic low back pain is admitted to the hospital
for abdominal pain lasting 2 days. He denies fever,
chills, or sick contacts. His last bowel movement
was 3–4 days ago. On examination, he is afebrile
and has moderate left upper and lower quadrant
tenderness. An abdominal radiograph reveals
large amounts of stool in the colon with no signs
of obstruction. He currently takes lisinopril 20 mg/
day, verapamil 240 mg once daily, acetaminophen
500 mg four times daily, oxycodone sustained
release 20 mg twice daily, and oxycodone/acet-
aminophen 5/325 mg as needed for pain. His SCr
is 1.8 mg/dL (baseline 1.7 mg/dL). Which therapy
would best manage this patient’s constipation?
A. Sodium phosphate oral solution.
B. Bisacodyl suppository.
C. Methylcellulose tablets.
D. Methylnaltrexone injection
A
- Answer: B
This patient presents with acute constipation given his
symptoms of abdominal pain, both by complaints and
on examination; reduced frequency of bowel move-
ments; and radiographic evidence of a large quantity
of stool in the colon. Contributing factors include the
use of verapamil and oxycodone without the use of a
drug regimen to prevent constipation. Therapy should
be instituted to provide a quick onset to initiate a bowel
movement and provide symptom relief. Saline laxatives
such as sodium phosphate (Answer A) provide quick
results, especially when given by enema. The oral for-
mulation of sodium phosphate results in phosphate
absorption and is problematic in patients with chronic
kidney disease. This patient’s CrCl is about 34 mL/minute/1.73 m2
, so saline laxatives should be avoided.
Bisacodyl suppositories (Answer B) provide rapid stim-
ulation of the lower intestinal tract without the risk of
electrolyte absorption, so they would be preferred in
this case. Methylcellulose (Answer C) is a bulk-form-
ing laxative that would not treat the patient’s acute
constipation, but it would be an option for preventing
constipation on a long-term basis in this patient once
the short-term episode is resolved. Although methyln-
altrexone (Answer D) is indicated for opioid-induced
constipation, it would generally not be used as first-line
agent, given the need for injection and the added cost
compared with traditional laxatives.
13
Q
- A 65-year-old man (height 68 inches, weight 79
kg) with a history of hypothyroidism, heart failure,
and MI is admitted to the intensive care unit with
severe community-acquired pneumonia. Six hours
after admission, he develops acute respiratory fail-
ure, hypotension, and acute kidney injury from
presumed sepsis. Mechanical ventilation is imple-
mented, and an NG tube is placed. He currently
takes ramipril 10 mg/day, metoprolol 100 mg twice
daily, levothyroxine 125 mcg/day, and aspirin 81
mg/day. His WBC is 25 × 103
cells/mm3
, platelet
count is 170,000/mm3
, SCr is 3.8 mg/dL (base-
line 1.1 mg/dL), potassium is 4.9 mEq/L, BUN is
65 mg/dL, international normalized ratio (INR)
is 1.1, AST is 30 IU/mL, and ALT is 45 IU/mL.
Which approach is most appropriate for prevent-
ing stress-related mucosal disease (SRMD) in this
patient?
A. Sucralfate 1 g four times daily by NG tube.
B. Magnesium hydroxide 30 mL four times daily
by NG tube.
C. Cimetidine 8-mg/hour intravenous infusion.
D. Pantoprazole 40 mg intravenously once daily
A
- Answer: D
Stress-related mucosal disease develops in critically
ill patients and can lead to significant upper GI bleed-
ing. Therapy initiation to prevent SRMD is based on
the presence of risk factors. Independent risk factors
include mechanical ventilation and coagulopathy. This
patient is currently receiving mechanical ventilation and
has other risk factors such as sepsis, hypotension, and
acute renal insufficiency; therefore, he would meet the
criteria for initiating pharmacologic prophylaxis. Both
H2
RAs and PPIs are viable first-line options. Cimetidine
(Answer C) carries an FDA-approved indication for the
prevention of SRMD; however, the dosing provided is
incorrect because 50 mg/hour is the approved dose.
Likewise, cimetidine would need to be dose adjusted
for the patient’s CrCl, which can be assumed less than
10 mL/minute/1.73 m2
. Pantoprazole (Answer D) would
be a better choice in this case, and it does not require
adjustment for the CrCl. Sucralfate (Answer A) has his-
torically been used to prevent SRMD, but it has fallen
out of favor because of the need for multiple daily dos-
ing and the risk of aluminum accumulation in patients
with kidney disease. Antacids such as magnesium
hydroxide (Answer B) are not as effective as H2
RAs,
require multiple daily dosing, and are associated with
electrolyte accumulation in patients with kidney injury
14
Q
- A newly available NSAID was designed to reduce
the incidence of adverse GI events compared
with traditional NSAIDs. A large retrospective
cohort study compares the incidence of ulcer-
ation and bleeding associated with the use of this
new NSAID with the incidence of ibuprofen and
naproxen. The results indicate that the new agent
is associated with no statistically or clinically
significant reduction in ulceration or bleeding
with long-term use compared with ibuprofen and
naproxen. The investigators of the study argue that
the lack of difference in safety is because the drug
is being promoted as safer; therefore, most patients
receiving it are at a much higher baseline risk of
NSAID-induced ulceration and bleeding. If this
phenomenon did indeed affect the study results,
which potential source of bias would most likely be
present?
A. Recall bias.
B. Misclassification bias.
C. Interviewer bias.
D. Channeling bias.
A
- Answer: D
Several different forms of bias exist that can adversely
affect the validity or results of a trial. Errors in sam-
pling or measurement, incorrect patient enrollment
methods, and differences in patient populations stud-
ied in a trial are examples of areas of study design
and conduction that may introduce bias. When evalu-
ating drug literature, an important aspect of deciding
whether the reported results are valid is to recognize
important causes of bias. A retrospective cohort design
typically uses medical records to evaluate events that
occurred in the past after exposure to a drug. Recall
bias (Answer A) pertains to study outcomes or events
that patients are asked to recall, with results differing
depending on the ability of patients to remember an
event. For this study, objective documentation of ulcer-
ation or bleeding was performed to make comparisons
between groups, eliminating patient recall as a poten-
tial bias. Misclassification bias (Answer B) is typically
problematic in case-control studies, in which patients
can be entered in the case study group but have not
actually been exposed to the drug in question, which
would not be applicable in this case. Interviewer bias
(Answer C), or observer bias, is typically problematic
in direct patient survey studies; it pertains to variation
in the way different investigators collect data within a
trial. To eliminate this bias, everyone involved in data
collection in a study should be trained in the same
manner of data collection to maintain consistency.
Again, because an objective measure of GI toxicity was
recorded by endoscopy, the possibility of interviewer
bias is minimized. Channeling bias (Answer D) is a
form of allocation bias in which medications with sim-
ilar therapeutic indications are administered to patients
with differing prognoses or risk levels. Should claims
be made that a new drug introduced to a therapeutic
class has a particular advantage—in this case, a safer
GI toxicity profile—the chance that use will be chan-
neled to high-risk patients is much greater. Given that
the drug may be studied in higher-risk patients rather
than those in the comparator group, the development of
more events in this newer drug group may mask poten-
tial differences in safety and cause these events to be
attributed to drug-induced toxicity.
15
Q
- A new enzyme immunoassay for HCV RNA has
a reported sensitivity of 95% and a specificity of
92%. If the prevalence of HCV in a cohort of 500
patients is 40%, which value best represents the
positive predictive value of this new test?
A. 75%.
B. 89%.
C. 92%.
D. 96%.
A
- Answer: B
Positive predictive value gives the proportion of patients
with a disease when the presence of the disease is
indicated by a diagnostic test. It is affected by disease
prevalence; thus, as disease prevalence falls, so does
the positive predictive value of the test. Using the sen-
sitivity, specificity, and prevalence, a 2 × 2 table can
be constructed. The positive predictive value is calcu-
lated by dividing the true positives by the sum of the
true and false positives. In this case, that would be 190/
(190 + 24) × 100 = 89% (Answer B). The total number
of patients who tested positive divided by the number who tested negative, 75% (Answer A), does not indicate
the positive predictive value of a test. Specificity deals
with the proportion of patients without the disease who
have a negative test result; it can be calculated by tak-
ing the number of patients not having the disease using
the gold standard who tested negative with the new test
(true negatives = 276). Next, divide this by the num-
ber of patients who truly had no disease using the gold
standard, 300, which incorporates the 24 patients who
tested positive with the new test but truly had no dis-
ease (i.e., false positives). Specificity = 276/(276 + 24)
= 92% (Answer C). The number of patients who tested
negative and had no infection divided by the total num-
ber of patients with no infection does not illustrate pos-
itive predictive value 276/(276 + 10) = 96% (Answer D).
