EBM - Evaluating a Prognostic Study

MUSM Libraries: Evaluating a PROGNOSTIC article

Appraise | Results | Finding articles

Appraise

What did they do? (Methods)
1. Was the sample of patients representative?
2. Were the patients significantly homogeneous with respect to prognostic risk?
3. Was follow-up complete?
4. Were objective and unbiased outcome criteria used?
5. If subgroups with different prognoses are identified: was there adjustment for important prognostic factors? was there vadidation in an independent group of "test-set" patients?
What was the answer? (Results)
1. How likely are the outcomes over time?
2. How precise are the estimates of likelihood?
What did they say about the answer? (Conclusion)
1. Do the results of the study support the author/s conclusions?
2. Does the conclusion reflect the discussion?
3. Are there study limitations, and do these impact the conclusions?
4. Are potential discrepancies mentioned?
What do I do with this information?
1. Were the study patients and their management similar to those in my practice?
2. Was the follow-up sufficiently long?
3. Can I use the results in the management of patients in my practice?

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Results

Prognosis of a disease refers to its possible outcomes and the likelihood that each one will occur.

Prognostic results are the numbers of events that occur over time, expressed in:

absolute terms: e.g. 5 year survival rate
relative terms: e.g. risk from prognostic factor
survival curves: cumulative events over time

A prognostic factor is a patient characteristic that can predict a patient's eventual outcome:

demographic: e.g. sex, age, race
disease-specific: e.g. tumor stage
comorbidity: other co-existing conditions

Articles that report prognostic factors often use two independent patient samples:

derivation sets asks - "what factors might predict patient outcomes?"
validation sets ask - "do these prognostic factors predict patient outcomes accurately?"

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Finding articles about a prognosis study

PubMed:

Select PubMed@Mercer and click on Clinical Queries, perform a search, then choose Prognosis from Category
Select PubMed@Mercer and enter your search term/s AND (cohort studies OR "Prognosis"[Mesh])

References:

JAMA 1994 272:234-237
ACP Journal Club 1995 July-Aug; A12 - A14

From: Guyatt, G. Users' Guides to the Medical Literature: Essentials of Evidence-based Clinical Practice. AMA Press, 2002 and Straus. Evidence-Based Medicine. How to Practice and Teach EBM. Churchill-Livingstone, 3rd edition, 2005 (pocket cards).

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