【正文】 use likelihood ratio (LR)? Test Clinical value Meaning Stability with changing prevalence Can use multiple levels of a test result Sensitivity Specificity No Yes No Predictive value Yes No No Likelihood ratio Yes Yes Yes How to calculate and use positive and negative likelihood ratio? Posttest odds = pretest odds x LR Positive LR (LR+) = sensitivity / (1specificity) Negative LR (LR) = (1sensitivity) / specificity 註 Odds = p / 1p。 probability = odds / 1+odds 例如 : 和信鯨贏球的機(jī)率為 80%, 則鯨隊(duì)贏球的勝算為 4:1=4 LR = probability that finding is present in patients with disease probability that finding is present in patients without disease 診斷的過程是一連串機(jī)率的改變 … 一位 68歲女性 , 在最近一週來發(fā)生咳嗽有痰的情形 , 您認(rèn)為她罹患肺結(jié)核的可能性有多高 ? 診斷的過程是一連串機(jī)率的改變 … 0% 100% 95% 以往有肺結(jié)核的病史 咳痰僅一週 午間發(fā)燒 夜間盜汗 體重沒有減輕 胸部 X光顯示 : 右上葉肺炎浸潤 痰液 AFB smear顯示 AFB(+) P5 x LR5 = P6 What were the results? Of total 338 patients with plete study forms, valid lab results, and sufficient information for final diagnoses, 72 (21%) were considered to have active TB. EMTD test AFB smear Clinical Suspicion Level Clinical Suspicion Level Low Intermediate High Low Intermediate High N 224 68 46 N 224 68 46 LR+ 28 150 174 LR+ 10 LR LR How to Interpret a likelihood ratio: Likelihood ratio Interpretation 10 Strong evidence to rule in disease 5 –10 Moderate evidence to rule in disease 2 – 5 Weak evidence to rule in disease – No significant change in the likelihood – Weak evidence to rule out disease – Moderate evidence to rule out disease Strong evidence to rule out disease 0 20 40 60 80 100 Positive predictive Value , % Positive predictive Value Enhanced Mycobacterium tuberculosis AcidFast Bacilli Smear 0 20 40 60 80 100 Negative predictive Value , % Negative predictive Value Clinical Suspicion of Tuberculosis Low Intermediate high overall Low Intermediate high overall Other important results in this study ? For the low clinical suspicion group, both tests were useful for ruling out disease。 Neither proved convincing evidence for ruling in disease. ? For high suspicion group, both tests were useful for ruling in disease。 However, the PV of AFB smear was only 37%, pared with 91% for the EMTD. ? EMTD offers greatest utility in the intermediate suspicion group: ? The TB and nonTB cases were equally likely to have a positive AFB smear ? The prevalence of the suggestive CxR, cough and weight loss were also similar ? Mycobacteria other than TB were cultured more monly Step 5: 我該如何利用臨床研究的結(jié)果照顧我的病人 ? Will the results help me in caring for my patients? ? Will the reproducibility of the test result and its interpretation be satisfactory in my setting? Poor reproducibility are due to ? Problems of the test itself Ex. RIA kits for hormone levels ? Expertise is required in performing or interpreting the test Ex. Cardiac echo, abdominal sono, V/Q scan. Are the results applicable to my patients? ? Test properties may change in different subpopulations ? Practice in a similar setting ? Meet all the inclusion criteria ? Not violate any of the exclusion criteria ? Are there pelling reasons that the results should not be applied? ? Severity of diseases ? Mix of pelling conditions ? The issue of generalizability may be resolved if you can find an overview that pools the results of a number of studies Will patients be better as a result of the test? ? The usefulness of a diagnostic test depends on ? Whether it adds information beyond that otherwise available ? Whether this information leads to a change in management that is ultimately beneficial ? In some situation, tests may be accurate, management may even change, but their impact on patient oute may be far less certain. Ex. Right heart catheterization for critically ill patients 試著思考下列問題 : 參加研究，轉(zhuǎn)介納入病人的均為對(duì)診治肺結(jié)核很有經(jīng)驗(yàn)的胸腔科或感染科醫(yī)師；將本研究的結(jié)果應(yīng)用在我們平常臨床照護(hù)上有什麼該注意的呢？ Turning back to our patient… 由以上可知 : 在臨床上懷疑罹患肺結(jié)核可能性較低的族群中 , 痰液 AFB染色陽性者其罹患肺結(jié)核的機(jī)率不到 40%。 這時(shí)有什麼辦法來幫助我們提高肺結(jié)核的診斷率 ?? 多重試驗(yàn) (平行試驗(yàn)或序列試驗(yàn) ) 在此時(shí)有幫助嗎 ? 若 TBPCR的結(jié)果為陰性 (或陽性 ), 對(duì)我們的處理有什麼影響 ? Evidence is never enough… ? 利用 CSF TBPCR檢查 快速診斷結(jié)核性腦膜炎 ? J Clin Microbiol 1998。 36: 1251 1254 ? J Clin Microbiol 2021。 38: 3150 – 3155 ? 利用 TBPCR檢查 診斷結(jié)核性肋膜炎及其他肺外結(jié)核 ? Chest 1998。 113: 1190 1194 ? Chest 2021。 119: 1737 1741 How To Use Articles about Clinical Predication Rules Examples for evidencebased practicing 臺(tái)大內(nèi)科 張家勳 / 楊泮池教授 Email: Clinical scenario 林同學(xué) , 20歲男性 , 這次來急診的主述為三天來持續(xù)發(fā)燒 , 同時(shí)合併咳嗽有黃痰和氣促 ? 10 天前開始輕微發(fā)熱、喉嚨痛、及流鼻水 ? 除過敏性鼻炎外 無其他重大疾病 ? 否認(rèn)在過去二週內(nèi)曾出國旅遊 ? 理學(xué)檢查 : 130/85 mmHg, 38℃ , 100, 20。 no wheezing ? WBC 18000。CxR: pneumonic patch over R’t lower lung 要不要安排林同學(xué)住院呢 ? 實(shí)際上常面臨的情況 ? 經(jīng)驗(yàn)有限 … ? 沒有一致地、完整地追蹤病人 ? 過於強(qiáng)調(diào)特殊的案例 ? 不容易了解個(gè)別特徵 (即預(yù)後因子 ) 與其他特徵間的相互關(guān)係 ? 難以評(píng)估個(gè)別因子 以及與其他因子相互作用下 對(duì)病人預(yù)後的整體影響 What we will learn today… ? Step 1: 如何明確的分析我們所面臨的臨床問題 ? ? Step 2: 證據(jù)在哪裡 ? 如何有效率的搜尋文獻(xiàn) ? Step 3: 臨床研究的結(jié)果可信嗎 ? ? Step 4: 其臨床意義為何 ? ? Step 5: 我該如何利用臨床研究的結(jié)果照顧我的病人 ? Step 1: 如何明確的分析我們所面臨的臨床問題 ? The Specific, Answerable Clinical Question: ? Patients: 罹患社區(qū)性肺炎的病人 ? Intervention: WBC 高的患者 (eg, 15,000) ? Comparison: WBC 不高的患者 ? Outes: 死亡率是否顯著高了許多 … The Specific, Answerable Clinical Question: ? Patients: 罹患社區(qū)性肺炎的病人 ? Intervention: Clinical prediction rule ? Comparison: 醫(yī)師的經(jīng)驗(yàn)或直覺 ? Outes: 準(zhǔn)確預(yù)測(cè)住院期間發(fā)生 mortality amp。 morbidity 減少不必要的住院 但是不會(huì)降低照護(hù)的品質(zhì) … What Are Clinical Prediction or Clinical Decision Rules (CPR。 CDR) ? Tools that quantify the individual contributions