尿液試紙有助於預測急性腎臟損傷


  【24drs.com】根據發表於國家腎臟基金會(NKF)2012春季臨床會議的研究結果,一種常用的尿液試紙可以預測急性腎臟損傷(acute kidney injury,AKI)。校正干擾因素之後,研究者發現,住院後72小時內試紙檢查發現尿蛋白的病患,發生AKI的風險是試紙無反應患者的2倍 (勝算比[OR]2.3,95%信心區間1.4-3.8)。
  
  美國密西根底特律亨利福特醫院內科住院醫師Javier Neyra表示,尿蛋白試紙是一種便宜、簡單、迅速、非侵犯性、廣泛可取得的診斷檢測工具,可作為重症敗血病患的早期AKI生物標記。
  
  試紙尿蛋白檢測是例行尿液分析的一項,對於特定患者,普遍用它來辨識是否有源自泌尿系統的感染;嚴重敗血病和微白蛋白尿患者約有3/10發生AKI,敗血症病患多達87%曾發生。
  
  Neyra醫師表示,急性或嚴重敗血症患者預期會發生蛋白尿。動物研究顯示,敗血症中,腎小管傷害意味著蛋白質再吸收受損。最近的其他研究認為,敗血症時活化的一個基因可能會分泌更多蛋白質。
  
  為了確認試紙尿蛋白檢測對於作為敗血症相關AKI的生物標記有多好,研究者回溯分析2004年1月至2011年7月間住進亨利福特醫院加護病房的328名嚴重敗血症病患、以及住院時進行試紙尿蛋白檢查的資料,開始時血清肌酸酐值大於1.5 mg/dL且住院3個月內進行試紙尿蛋白檢查者、常引起偽陽性試紙尿蛋白的原因,如泌尿道感染或肉眼性血尿,則排除於研究。
  
  64%的病患在住院72小時內、血清肌酸酐值增加至少0.3 mg/dL,這些病患有114人(54%)新發生試紙尿蛋白(P< 0.001;陽性預測值75%),166名AKI病患(依據急性腎臟損傷網絡規範)中則有91人(55%)發生(P= 0.002;陽性預測值60%)。
  
  Neyra醫師表示,重點在辨識生物標記即時且早期診斷AKI的敏感性與特定性。他解釋,傳統方法依賴血清肌酸酐值偵測敗血症病患的AKI可能會延誤診斷,一部分是因為敗血症病患肌肉產生的肌酸酐值較低,此外,敗血症病患接受積極的靜脈輸注,可能會稀釋了血清肌酸酐。
  
  NKF理事長、位於Morrisville的合約研究機構、Pharmaceutical Product Development 藥物主動監測醫療主任Lynda Szczech醫師表示,試紙尿蛋白的效果相當好。
  
  Szczech醫師表示,這個工具可以發現哪些人比較可能發生AKI,並幫助照護者及早介入與預防發生。她知道這還不是最好,但是其他試圖研發的生物標記也有類似問題。這是一種相當便宜、簡單、例行性的輔助血清肌酸酐測量,對於一個我們如何運用這樣一個常用的東西,有提出明確的觀察。
  
  Szczech醫師指出,對於腎功能惡化,肌酸酐不是個好標記,她解釋,將一個人的兩顆腎臟都取出一整天,但是不會立即顯示出受傷,因為肌酸酐值需要24小時以上才會升高。
  
  生物標記並非可完全信賴;開始時的腎臟壓力會導致未發生腎臟損傷者的數值升高。持續發生AKI者的生物標記也可能不會升高,沒有哪種生物標記是完美的。
  
  她指出,我們仍舊在尋找腎臟的肌鈣蛋白。當肌鈣蛋白升高,你知道你心臟病發作。如果它沒升高,你沒有發生心臟病發作。雖然研究者正尋找有用的生物標記,它們或許只能在一種情況有用,但是可以彌補彼此的缺點。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_idno=6821&x_classno=0&x_chkdelpoint=Y
  

Urine Dipstick Helps Predict Acute Kidney Injury

By Sandra Yin
Medscape Medical News

May 15, 2012 (Washington, DC) — A commonly used urine dipstick can predict acute kidney injury (AKI), according to findings presented here at the National Kidney Foundation (NKF) 2012 Spring Clinical Meetings.

After adjustment for confounders, researchers found that patients who developed dipstick proteinuria had more than double the risk of developing AKI in the first 72 hours of admission than those who did not (odds ratio [OR], 2.3, 95% confidence interval, 1.4 to 3.8).

"Dipstick proteinuria is a cheap, simple, rapid, noninvasive, and widely available diagnostic test that could serve as an early biomarker of AKI in critically ill septic patients," lead researcher Javier Neyra, MD, an internal medicine resident at Henry Ford Hospital in Detroit, Michigan, told Medscape Medical News.

Checking for dipstick proteinuria is a component of the routine urinalysis. In septic patients, it is commonly used to identify whether an infection originated in the urinary system. AKI occurs in nearly 3 of 10 patients with severe sepsis and microalbuminuria, and has been noted in up to 87% of septic patients.

Proteinuria in patients with acute or severe sepsis is to be expected, Dr. Neyra said. Animal studies have shown that in sepsis, tubular damage in the kidney means that reabsorption of protein is impaired. Other recent studies have suggested that a gene that can be activated in sepsis might secrete more protein.

To determine how good an early biomarker of sepsis-related AKI de novo dipstick proteinuria is, the researchers retrospectively analyzed data from 328 patients with severe sepsis who were admitted to the intensive care unit at Henry Ford Hospital from January 2004 and July 2011 and who underwent dipstick proteinuria testing on admission. Patients whose baseline serum creatinine level was above 1.5 mg/dL and who had dipstick proteinuria within 3 months of the index admission date and common causes of false-positive dipstick proteinuria, such as urinary tract infection or gross hematuria, were excluded from the study.

Serum creatinine increased at least 0.3 mg/dL in 64% of patients within the first 72 hours of admission. New-onset dipstick proteinuria was found in 114 (54%) of those patients (P < 0.001; positive predictive value, 75%) and in 91 of 166 (55%) patients with AKI, based on Acute Kidney Injury Network criteria (P = 0.002; positive predictive value, 60%).

It is important to identify biomarkers that are sensitive and specific and that provide timely and early diagnosis of AKI, Dr. Neyra said. The traditional approach of relying on serum creatinine levels to detect AKI in septic patients can delay its diagnosis, he explained, in part because creatinine production from muscle is lower in septic patients. In addition, septic patients receive aggressive intravenous fluid administration, which can dilute serum creatinine.

NKF president Lynda Szczech, MD, MSCE, FASN, FNKF, medical director of pharmacovigilance at Pharmaceutical Product Development, a contract research organization based in Morrisville, North Carolina, told Medscape Medical News that the performance of the dipstick proteinuria is "remarkably good."

The tool, Dr. Szczech said, can detect who is most susceptible to AKI and help providers intervene early and prevent it from developing. She acknowledged that it is not perfect, but explained that all the other biomarkers that people are trying to develop have similar issues. This is "a really cheap, easy, routinely measured adjunct to serum creatinine and is actually a brilliant observation on how to use something that we would use anyway."

Creatinines are a notoriously bad marker for kidney function, noted Dr. Szczech. A person could have both kidneys taken out one day, but the manifestation of injury wouldn't be immediately apparent, because creatinine levels might not be elevated for 24 hours or more, she explained.

Biomarkers are not totally reliable, she said; baseline renal stress can lead to elevations in people who do not go on to develop kidney injury. Biomarkers might also not be elevated in people who go on to develop AKI. "None of the biomarkers are perfect," she said.

"We're still looking for the troponin of the kidney." When troponin goes up, you know you've had a heart attack. If it doesn't go up, you haven't had a heart attack, she explained. Although researchers are looking at promising biomarkers, they will probably "only have promise when used in a panel so they can complement each others' weaknesses," she added.

Dr. Neyra has disclosed no relevant financial relationships. Dr. Szczech works for Pharmaceutical Product Development.

National Kidney Foundation (NKF) 2012 Spring Clinical Meetings. Poster 17. Presented May 10, 2011.

    
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