HALLO
Learn more second part - Causation, Etiology & Harm
Which study design do you think provide best evidence for relating a possible cause to an adverse clinical outcome – e.g. tobacco smoking and implant bone loss?
(A cohort of) patients are examined prior to receiving implants and followed over time prospectively – if the tobacco smokers loose more bone than the non-smokers there is likely a causal relationship.
(A cross-section of) patients is examined. Those with extensive bone loss around implants are contrasted to those with minimal bone loss – if the proportion of tobacco smokers is higher there is likely a causal relationship.
(A cohort of) patients are examined at e.g., 3 or 5 years after (retrospectively) having received dental implants – if the tobacco smokers have lost more bone than the non-smokers there is likely a causal relationship.
Patients with extensive bone loss (cases) are contrasted to patients with minimal bone loss matched by age, gender and treatments (controls)– if the proportion of tobacco smokers is higher there is likely a causal relationship .
HOWEVER – There are Good, Bad and Ugly Observational studies. These can be recognized by applying the Newcastle-Ottawa scale