Lecture 4: Case Study: NAION Flashcards Preview

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Flashcards in Lecture 4: Case Study: NAION Deck (13):


Drug class (PDE5 inhibitor) is taken on an as-needed basis for the treatment of erectile dysfunction. When study was initiated, there were only 3 PDE5 inhibitors on the market
NAION is a rare visual disorder presenting as a sudden partial loss of vision in one eye (incidence: 2.5 - 11.8 per 100,000 men aged 50+)
Post approval: cases of NAION seen in men using PDE5 inhibitors
NAION and ED share several risk factors including diabetes, hyperlipidemia and smoking


Research Question

To determine whether recent exposure to PDE5 inhibitors is associated with onset of NAION (acute effect or class effect)


What information is needed?

1) Risk of NAION in ppl exposed to PDE5i
2) Risk of NAION in people exposed to PDE5i if they had not been exposed (use risk of NAIONi in ppl unexposed)


Case crossover design advantages

controls for confounding effects that were a concern, avoids potential biases associated with control selection since cases serve as their own controls
compare exposure and outcome with OR


Case Crossover design (Case window)

time interval just prior to disease onset (exposed)


Case Crossover design (Control window)

time period prior to case window divided into discrete independent intervals (unexposed)


NAION Study strategy

Data source: Primary data required because secondary data not feasible
Study Design: Case crossover used because cohort design not feasible (rare endpoint, expensive) and case control leaves you with too much confounding


Study Population

potential cases enrolled by 100+ ophthalmologists in US and Europe 2008-2012 (enrolled solely based on ophthalmologic criteria and irrespective of PDE5i exposure status


Measurement of Outcome (NAION)

1) Cases were adjudicated by expert committee with extensive experience in NAION diagnosis (cases classified as Definite, possible, or non-NAION)
2) PDE5i exposure status was also masked from committee


Measurement of Exposure (PDE5i)

PDE5i taken as needed for treatment of ED and must b obtained by subject self-report, so they needed STANDARDIZED approach to maximize accuracy
In the end PDE5i use obtained via telephone interview call center


Phone Interview Questions

1) Participants were asked to recall dates of use during 2 months prior to NAION onset
2) They were asked about their prior use of several types of medications to avoid recall bias due to knowledge of research question.
3) Accuracy of recall improved via calendars, questions about average use and timing of significant life events (birthdays, trips)



Primary analysis: 43 definite NAION cases (1247 controls, OR = 2.15)
Sensitivity analysis: 64 definite and possible NAION cases (1856 controls and OR = 2.36)



1) Results indicate a 2-fold increased risk of NAION associated with recent use of PDE5i
2) Bias from inaccurate recall was unlikely to have substantially affected results
3) Weekly use of PDE5 inhibitors estimated to add 3 NAION cases per 100,000 men aged 50+ years each year