Nemat Hashim, Khan Rabia, Ashraf Muhammad Salman, Matta Mandeep, Ahmed Shahin, Edwards Barbara T, Hussain Roshan, Lesser Martin, Pekmezaris Renee, Dlugacz Yosef, Wolf-Klein Gisele
Long Island Jewish Medical Center, New Hyde Park, New York 11040, USA.
Am J Gastroenterol. 2009 Aug;104(8):2035-41. doi: 10.1038/ajg.2009.174. Epub 2009 Apr 14.
There has been a significant increase in the prevalence, severity, and mortality of Clostridium difficile infection (CDI), with an estimated three million new cases per year in the United States. Yet diagnosing CDI remains problematic. The most commonly used test is stool enzyme immunoassay (EIA) detecting toxin A and/or B, but there are no clear guidelines specifying the optimal number of tests to be ordered in the diagnostic workup, although multiple tests are frequently ordered. Thus, we designed a study with the primary objective of evaluating the diagnostic utility of repeat second and third tests of stool EIA detecting both toxins A and B (EIA (A&B)) in cases with negative initial samples, and sought to describe the physicians' patterns of ordering this test in the workup of suspected CDI.
A retrospective study was carried out using a database of all stool EIA (A&B) tests ordered for a presumptive diagnosis of CDI. All patients were adults admitted to a major teaching hospital over a three-and-a-half-year period (tests completed within 5 days of ordering the first test were grouped into a single episode, and only the first three samples per episode were analyzed). Age, gender, and results of stool EIA were tabulated. In addition, physicians' ordering patterns and proportion of positive stools relative to the number of tests ordered were also analyzed. A single positive EIA result was interpreted as evidence for the clinical presence of CDI.
A total of 3,712 patients contributed to 5,865 separate diarrhea episodes (total stool EIA (A&B)=9,178), and 1,165 (19.9%) of these episodes were positive for CDI. Of the positive patients, 73.2% were over the age of 65 years and 54.2% of them were females. The most frequent ordering pattern for presumptive CDI was a single stool test (60.1%), followed by two more tests (23.2%). Three tests were still ordered in 16.6% of the cases. Of the 1,165 positive cases, 1,046 (89.8%) were diagnosed in the very first test, 95 (8.2%) in the second, and only 24 (2.0%) in the third test. In 1,934 instances, a second test was ordered after an initial negative result, of which 95 (4.91%) became positive. In 793 episodes, a third test was ordered after two negative samples, of which only 24 (3.03%) became positive.
This study highlights the low diagnostic yield of repeat stool EIA (A&B) testing. Findings strongly support the utility of limiting the workup of suspected CDI to a single stool test with only one repeat test in cases of high clinical suspicion, and avoiding the routine ordering of multiple stool samples. As Clostridium difficile is becoming an endemic health-care problem resulting in major financial burdens for the US health-care system, clear guidelines specifying the optimal number of stool EIA (A&B) tests to be ordered in the diagnostic workup of suspected CDI must be established to assist physicians in the practice of evidence-based medicine.
艰难梭菌感染（CDI）的患病率、严重程度和死亡率显著上升，在美国估计每年有300万新发病例。然而，CDI的诊断仍然存在问题。最常用的检测方法是粪便酶免疫测定（EIA），用于检测毒素A和/或B，但目前尚无明确指南规定在诊断检查中应进行的最佳检测次数，尽管经常会进行多次检测。因此，我们设计了一项研究，其主要目的是评估在初始样本为阴性的情况下，重复进行第二次和第三次粪便EIA检测毒素A和B（EIA（A&B））的诊断效用，并试图描述医生在疑似CDI检查中开具此项检测的模式。
利用为疑似CDI的初步诊断而进行的所有粪便EIA（A&B）检测的数据库开展一项回顾性研究。所有患者均为在三年半时间内入住一家大型教学医院的成年人（在首次检测下单后5天内完成的检测归为一个单次事件，每个事件仅分析前三个样本）。记录年龄、性别和粪便EIA检测结果。此外，还分析了医生的开具检测模式以及阳性粪便相对于开具检测次数的比例。单个阳性EIA结果被视为CDI临床存在的证据。
共有3712例患者出现5865次单独的腹泻事件（粪便EIA（A&B）检测总数=9178次），其中1165次（19.9%）腹泻事件CDI检测呈阳性。在检测呈阳性的患者中，73.2%年龄超过65岁，其中54.2%为女性。疑似CDI最常见的开具检测模式是单次粪便检测（60.1%），其次是再进行两次检测（23.2%）。16.6%的病例仍进行了三次检测。在1165例阳性病例中，1046例（89.8%）在首次检测时被诊断出来，95例（8.2%）在第二次检测时被诊断出来，只有24例（2.0%）在第三次检测时被诊断出来。在1934例情况下，首次检测结果为阴性后又进行了第二次检测，其中95例（4.91%）转为阳性。在793次事件中，两次样本检测均为阴性后又进行了第三次检测，其中只有24例（3.03%）转为阳性。
本研究突出了重复粪便EIA（A&B）检测的低诊断率。研究结果有力地支持了将疑似CDI的检查限于单次粪便检测，对于临床高度怀疑的病例仅进行一次重复检测，并避免常规开具多个粪便样本检测的做法。由于艰难梭菌正成为一个医疗卫生领域的地方性问题，给美国医疗卫生系统带来重大经济负担，因此必须制定明确的指南，规定在疑似CDI的诊断检查中应进行的最佳粪便EIA（A&B）检测次数，以帮助医生实施循证医学实践。
