Clinical Scenario. Step 1: Ask an answerable clinical question--P. I. C. O. Patient / Problem : Intervention / Exposure: Comparison: Outcome:. PICO. Question: Patient / Problem : Intervention / Exposure: Comparison: Outcome:.
Step 1: Ask an answerable clinical question--P. I. C. O.
Patient / Problem :
Intervention / Exposure:
Step 2: Effective searches for the best Evidence
Step 3: Critically appraise that evidence for its validity and importance
A.試驗結果是確實的嗎？(內部正當性) Are the results of the trial valid?
理想上希望診斷試驗可以應用在所有病患身上-- 包括標的疾病輕微時、嚴重時，及早期和晚期的病患身上。最好患者是隨機選取或連續選取，以便將選取誤差減到最小。 It is ideal if the diagnostic test is applied to the full spectrum of patients - those with mild, severe, early and late cases of the target disorder. It is also best if the patients are randomly selected or consecutive admissions so that selection bias is minimized.
Level of evidence:
Full spectrum of spectrum ? Yes□ No□ Unclear□
Randomly selected or consecutive patients ? Yes□ No□ Unclear□
理想上，研究中索引試驗和參考標準試驗都應該在所有患者執行。在參考標準試驗是侵入性或昂貴的情況下，倘若索引試驗結果是陰性的(因此，一個低可能性的疾病)，此時是否要執行參考標準試驗可能會有所保留。另一個可選擇的參考標準是需要有適當時期追蹤(視個別疾病而定)來檢視他們是不是真的是陰性的(沒標的疾病的)。 Ideally both the index test and the reference standard should be carried out on all patients in the study. In some situations where the reference standard is invasive or expensive there may be reservations about subjecting patients with a negative index test result (and thus a low probability of disease) to the reference standard. An alternative reference standard is to follow-up people for an appropriate period of time (dependent on disease in question) to see if they are truly negative.
Both the index test and the reference standard carried out on all patients in the study ? Yes□ No□ Unclear□
Or follow-up people for an appropriate period of time ?Yes□ No□ Unclear□
首先，參考標準應該是適當的-與“真相”儘可能接近。有時候, 單一個參考標準可能不完全恰當的，可能要多個試驗合併來表示疾病的陽性。其次， 參考標準和索引試驗應該獨立且雙盲地執行在病患身上。判讀某一個試驗的結果的人,不能知道另一試驗的結果。 First the reference standard should be appropriate - as close to the 'truth' as possible. Sometimes there may not be a single reference test that is suitable and a combination of tests may be used to indicate the presence of disease. Second, the reference standard and the index test being assessed should be applied to each patient independently and blindly. Those who interpreted the results of one test should not be aware of the results of the other test.
Was the reference standard appropriate ?Yes□ No□ Unclear□
The reference standard and the index test being assessed applied to each patient independently and blindly ?Yes□ No□ Unclear□
3.索引與參考標準之間是否有一個獨立、雙盲的比較？Mbo - Was there an independent, blind comparison between the index test and an appropriate reference ('gold') standard of diagnosis?
B.試驗的結果為何(夠重要嗎)? What were the results?
敏感度(Sensitivity, Sn) =有此病的人測出陽性結 果的比率
特異度(Specificity, Sp) = 無此病的人測出陰性結果的比率
陽性預測值(PPV) = 試驗陽性的人有此病的比率
陰性預測值(NPV) = 試驗陰性的人無此病的比率
Sn = a/a+c
Sp = d/b+d
PPV = a/a+b
NPV = d/c+d
Step 4: Apply to your patient: Integrate with patients’ values and preferences
Is the diagnostic test available, affordable, accurate, and precise in our setting?
Can we generate a clinically sensible estimate of our patient’s pre-test probability (prevalence =a+c/a+b+c+d, from personal experience, prevalence statistics, practice databases, or primary studies)?
Are the study patients similar to our own?
Is it unlikely that the disease possibilities or probabilities have changed since this evidence was gathered?
Will the resulting post-test probabilities affect our management and help our patient?
Could it move us across a test-treatment threshold?
Would our patient be a willing partner in carrying it out?
Diagnostic test available, affordable, accurate, and precise in our setting?
The study patients similar to our own?
The disease possibilities or probabilities have changed since this evidence was gathered?
Pre-test probability (prevalence)= (a+c)/(a+b+c+d)
Post-test probability For LR+= a/(a+b) = PPV
Post-test probability For LR -= d/(c+d) - NPV