談"Target uncertainty"(目標不確定度)
今年(2014)六月TAF台北場的主管訓練丟出了"Target uncertainty"(目標不確定度)一詞，講義還清楚標記不依此方法做的，就會收到NCR。此事困擾不少聽過訓練課程的醫檢師。特此提出討論，讓大家有正確認知，以免被誤導。
廠商開發新試劑和實驗室自行開發檢驗方法時，必須做方法確認(Method validation, 以下簡稱MV)，MV需要CV和bias的允收標準(Acceptance criteria)，"Target
uncertainty"就是供method validation設定CV和bias的允收標準用的，所以才會有CV用1/3TEa，bias用1/4TEa的說法。(所謂的Top-down方法)
一般臨床實驗室大多使用廠商已確認的方法，所以不需做MV，只需做方法查證(Method verification)，查證對象是廠商所宣稱的CV和bias。臨床實驗室日常監控CV和bias時也須自訂CV和bias的允收標準，訂定的方法是利用QC data去計算，訂定出自己的允收標準，並不是採用target
uncertainty。要求臨床實驗室以Target uncertainty的程序訂定自己CV和bias的允收標準，實務上是不需要的。
Using target measurement uncertainty to determine fitness for purpose
Abstract
The methods an analytical laboratory uses must be
validated to be fit for purpose. The fitness for purpose of a quantitative
method used to determine the concentration of a substance when assessing
compliance to requirements can be described by the maximum measurement
uncertainty. This is called the target measurement uncertainty. Acceptance
criteria for precision and bias in the method validation are then established
in terms of the target measurement uncertainty. The target measurement
uncertainty can be decided by following a process which involves determining
the required concentration range of the measurand; determining the acceptable
level of risks of incorrect decisions of compliance; developing a suitable
decision rule, with guard bands if appropriate; using the probability of making
an incorrect decision of compliance based on the decision rule; and assessing
the impact of bias. A key participant in this process is the end user of the
data, the laboratory customer. This paper presents the concepts concerning
target measurement uncertainty introduced in recently published international
guidelines to the practicing analytical chemist who is not generally familiar
with these concepts. Three examples are used to illustrate the process.
