資料的評讀 III- 預後
神經內科 王志弘醫師
Prognosis
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預後
What’s going to happen to me?
Will I regain the function of my arm?
What is the prognosis in this patient with
metastatic lung cancer?
• What is the risk of stroke in a patient with
non-valvular atrial fibrillation?
Types of Reports
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Systemic review
Cohort study
Randomized trials
Case control studies
Cohort Study
Randomized Trials
Case Control Study
Validity
Impact
Applicability
正確性
效用
運用性
Validity
Are the results of this prognosis
study valid?
Representative Samples
• 代表性
– Disease spectrum
• 從疾病中的哪個時間點開始追蹤
– 整個研究所收錄的患者都能位在類似的疾病時
間點上 (類似的stage)
– Inception cohort
• （確定的）症狀開始出現的時間點
• 開始檢查或治療的時間點
• 越早越好
Follow Up
• 追蹤患者直到痊癒，或者發生特定的結果
（疾病、併發症、死亡）
• 追蹤時間
• 追蹤率，loss of follow up
– 死亡、疾病太嚴重無法來追蹤
– 搬家
– Loss <5%: little bias
– Loss >20%: 嚴重影響可信度
• “Best” or “Worst” cases
Outcome
• Outcome criteria
– 死亡
• The occurrence of death is objective, but judging the
underlying cause of death is prone to error.
– specific criteria to define each important outcome
• Blind
Prognostic Factors
• 預後因子
– Demographic (age, gender), disease specific (MVP
with MR), or co-morbid (HTN) variables that are
associated with the outcome of interest.
• 致病因子：直接引起疾病
• 危險因子
– Risk factors
– 環境、或是生活型態等因素，與疾病的生成有
關
Subgruop Analysis
• 是否重要的預後因子都有納入考慮，並予
以調整
– 分層分析
– 多變項分析
• 驗證預後因子
– 實驗組
– 驗證組
Impact
Is this valid evidence about
the prognosis important?
Results Format
• Percentage of survival at a particular time
point
– 1-year or 5-year survival rare
• Median survival ( the length that 50% patients
died)
• Survival curve
– Kaplan Meier curves
How Precise
• Confidence interval
• From our study, we found that age, male sex
(Hazard ratio 1.4) and functional impairment
(2.1 [1.6–3.3]) were predictors of mortality.
Education, social class and self-reported
health didn't predict mortality. Median
survival of male patients aged 70–79 was 4.6
years (3.0–8.6).
Applicability
Can we apply this valid,
important evidence about
prognosis to our patient?
Patient vs Study Group
• Difference is inevitable.
• Are the study patients so different from ours
that we should not use the results at all?
Impact on Decision Making
• Prognostic evidence
– for deciding whether or not to initiate therapy
– for monitoring therapy that has been initiated
– for deciding which diagnostic tests to order