鐵相關檢驗於診斷缺鐵性貧血的準確性及效益評估

Evaluation of the Accuracy and Efficiency of Iron-Related Tests in the Diagnosis of Iron Deficiency Anemia

溫武慶(Wu-Ching Uen) ； 林家義(Ka-Ee Ling)

《內科學誌》 16卷6期 (2005/12) Pp. 269-273

https://doi.org/10.6314/JIMT.2005.16(6).03

摘要

缺鐵性貧血(iron deficiency anemia，IDA)的實驗室檢驗包括血清鐵(serum Fe)，總鐵結合能(total iron binding capacity，TIBC)，鐵飽和度(Fe/TIBC)，鐵蛋白(serum ferritin)，血中溶解型運鐵蛋白接受體(soluble transferring receptor)，及骨髓含鐵量(iron store)等，較為普遍的檢驗為前四種。為找出較合乎經濟效益的檢驗方式，本研究探討並比較這些檢驗對於缺鐵性貧血診斷的靈敏度(sensitivity)、特異性(specificity)、陽性預測值(positive predictive value)、陰性預測值(negative predictive value)。
本研究自2004年一月至2005年八月間共蒐集有小球性紅血球病患223人作分析，其中缺鐵性貧血163人，其他貧血60人。結果顯示各檢驗對診斷缺鐵性貧血之靈敏度、特異度、陽性預測值、陰性預測值分別為(1)血清鐵（男≦45μg/dl，女≦30μg/dl）:75.46%、91.67%、96.09%、57.59%；(2)總鐵結合能＞428μg/dl:20.25%、100%、100%、31.58%；(3)鐵飽和度＜23%:96.32%、66.67%、88.70%、86.96%；(4)鐵蛋白（男≦30ng/dl，女≦17ng/dl）:91.41%、100%、100%、81.08%；分析結果以鐵蛋白的診斷準確性最高，鐵飽和度次之。如果同時檢驗鐵蛋白和鐵飽和度來作診斷，其靈敏度、特異度、陽性預測值、陰性預測值分別為99.39%、66.67%、89.01%、97.56%。雖增加了檢驗成本，但並未較只測定鐵蛋白優異。
對於小球性貧血疑缺鐵性貧血者之檢驗，建議應該先驗鐵蛋白即可。對少數鐵蛋白不低但仍高度懷疑有缺鐵性貧血（如有同時有慢性發炎疾病或肝疾病）者才再驗鐵飽和度，這是最準確且合乎經濟效益的診斷步驟。

關鍵字

缺鐵性貧血 ； 血清鐵 ； 總鐵結合能 ； 鐵飽和度 ； 鐵蛋白

並列摘要

Laboratory tests commonly used in diagnosing iron deficiency anemia (IDA) include serum iron, total iron binding capacity (TIBC), saturation of transferrin (serum iron/TIBC), serum ferritin. The accuracy and efficiency of these tests were investigated in this study. Patients with microcytic RBC were included, and tested for serum iron, TIBC, saturation of transferrin, and serum ferritin. The diagnostic criteria in each test is serum iron (male≦45μg/dl, female≦30μg/dl); TIBC＞428μg/dl; saturation of transferrin ＜23%; serum ferritin (male 30≦ng/ml, female≦17ng/ml). The diagnosis of IDA was further confirmed by iron therapeutic trial. The sensitivity, specificity, positive predictive value, negative predictive value of each test for the diagnosis of IDA were calculated within the group of patients. Two hundred and twenty three patients were enrolled (163 IDA, 60 non-IDA). The sensitivity, specificity, positive predictive value, and negative predictive value of each test were: (1) serum iron: 75.46%, 91.67%, 96.09%, 57.59%; (2) TIBC: 20.25%, 100%, 100%, 31.58%; (3) saturation of transferring: 96.32%, 66.67%, 88.70%, 86.96%; (4) serum ferritin; 91.41%, 100%, 100%, 81.08%, respectively. The serum ferritin is the most effective test for the diagnosis of IDA. Combining serum ferritin with serum iron or saturation of transferrin does not add to the accuracy but increases the expense. We recommend serum ferritin test as the best single test for IDA. In the minority of patients who have above-normal ferritin levels but are strongly suspicious of having IDA (such as those with chronic inflammatory diseases or liver diseases), adding saturation of transferrin test is beneficial at that time.

並列關鍵字

IDA ； Serum Fe ； TIBC ； Saturation of transferring, Fe/TIBC ； Serum ferritin