Start Every Multiple Choice Question With:
Age, Gender, Timeframe
A 44-year-old female is brought to the emergency room by her children because she has developed colicky epigastric pain over the past 3 hours. This is the second time she has had this pain. It occurred two months ago but resolved over one hour. She is otherwise well. She takes no medications or illegal drugs. She drinks alcohol only occasionally.
Vital signs: Temperature: 98.6 °F, HR: 88 /min, RR: 14 /min, BP: 128/87 mmHg, SaO2: 97%
Which of the following would have the lowest sensitivity and specificity in establishing the diagnosis?
A. Electrocardiogram (EKG)
C. Laboratory testing
D. Physical examination
E. Upper gastrointestinal endoscopy
SUMMARY: The single most important principle of diagnosis is that predictive value positive (PPV+) is proportional to prevalence x sensitivity. If you don’t understand this, then you will have a very difficult time answering clinical vignettes on your exams. The concept of “age/gender/timeframe” refers to these very powerful predictors of prevalence, which will help you immensely in finding the differential diagnosis on the exam.