Strengths & Limitations Flashcards
(30 cards)
Why is a Newcastle-Ottawa score of 9/9 important?
Indicates maximum quality on selection, comparability & outcome domains → low risk of bias for a cohort design.
Which three formal quality scores did you use to report this studu?
Newcastle-Ottawa = 9/9; Downs & Black = 24/28; Jadad = 1/5.
Largest methodological strength of this study (one phrase)?
Very large, prospective UK Biobank cohort with 17 926 pre-DM + 7 798 DM followed ≈ 10 y.
How did multiple 24-h recalls strengthen diet assessment?
Averaging up to 5 WebQs reduced day-to-day error and better reflected long-term intake.
Key statistical model used & why appropriate?
Cox proportional-hazards (time-to-event, handles censoring).
Name two covariate blocks included in Model 2.
Socio-demographics (income, TDI) and lifestyle (smoking, alcohol, PA) ± clinical history.
Follow-up duration (strength)?
Mean ≈ 9.9 y (pre-DM) / 9.6 y (DM) → captures incident CVD with latency.
What novel analyses added mechanistic depth?
Decomposition (dietary components) and mediation (serum biomarkers).
Give one example of a successful sensitivity test.
Excluding events within 2 y of baseline did not change uPDI or hPDI estimates.
How does stratified analysis add credibility?
Consistent associations across age, sex, income, BMI, etc. reduces concern of effect-modifier bias.
Main limitation related to diet measurement?
Self-reported 24-h recall → recall bias & portion size not captured.
Why can timing of biomarkers vs diet be a weakness?
Bloods drawn before diet survey → temporal mismatch weakens mediation causality.
Explain “residual confounding” in this context.
Even after extensive adjustment, unmeasured factors (e.g., sleep, stress) could influence CVD risk.
Selection bias introduced by attrition?
70 % of pre-DM and 75 % of DM excluded; remaining sample likely healthier & more health-conscious.
Generalizability caveat noted by authors?
UK Biobank is mostly White; associations may differ in other ethnicities.
Why were gestational-DM cases excluded, and why a limitation?
Different pathophysiology; but exclusion prevents insights for younger women.
Interpret Jadad 1/5 score for an observational study.
Low because Jadad is RCT-focused; not inherently a flaw but shows tool mis-fit.
What confounder was adjusted only for diabetes cohort?
Disease duration.
Why is single-country food environment both strength & weakness?
Uniform food supply aids internal validity, but limits cross-cultural relevance.
Potential implementation barrier from results?
Need to swap refined carbs/SSBs for whole-grains may be costly & require behaviour change support.
How does ‘healthy-volunteer bias’ affect findings?
UK Biobank participants are healthier & wealthier than average → may underestimate true risk.
List two cost-neutral strengths of study design.
(1) Uses routinely-linked ICD-10 hospital data; (2) Web-based diet recall saves resources.
Why is lack of portion-size data clinically relevant?
Makes it hard to translate quintile scoring into real-world serving advice.
Which exclusion criterion reduces reverse causality?
Dropping participants who developed CVD within 2 y of baseline.
