국내 대학병원에서 Clostridioides difficile 감염 환자의 대변 독소 효소면역검사와 질병 중증과의 상관성
Correlation Between Fecal Toxin Enzyme Immunoassays and Disease Severity in Patients with Clostridioides difficile Infection in a Korean University Hospital
가톨릭대학교 의과대학 인천성모병원 진단검사의학과1, 가톨릭대학교 의과대학 서울성모병원 진단검사의학과2, 가톨릭대학교 의과대학 인천성모병원 소화기내과3
Department of Laboratory Medicine1, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul; Department of Laboratory Medicine2, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul; Division of Gastroenterology, Department of Internal Medicine3, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, KoreaCorrespondence to:
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Lab Med Online 2021; 11(2): 124-131
Published April 1, 2021
Copyright © The Korean Society for Laboratory Medicine.
방법: 2015년 12월부터 2018년 5월까지 항생제 연관 설사가 의심되는 환자에서 시행한 대변 tcdB 핵산추출검사(Seeplex Diarrhea ACE kit, Seegene, Korea)에서 양성 그리고/또는 대변 C. difficile 독소 효소면역검사(VIDAS toxin A/B enzyme-linked uorescent assay, BioMerieux, France)에서 양성(equivocal 포함)인 91명의 환자의 후향적 진료기록 검토와 통계방법을 통해 C. difficile 감염의 중증도와 각 검사의 양성 여부의 연관성을 조사하였다.
결과: C. difficile tcdB 핵산추출검사에서 양성을 나타낸 88명의 환자에서 독소 효소면역검사 양성 여부는 ATLAS 점수와 연관성을 보였으나(P=0.005), CDAD 중증도(P=0.107)와 CDSS 점수(P= 0.534)와는 연관성을 보이지 않았다. 효소면역검사의 equivocal 결과를 양성에 포함시켰을 때 효소면역검사 양성 여부는 CDAD 중증도(P=0.03) 및 ATLAS 점수(P<0.001)와 연관성을 보였으나 CDSS 점수 (P=0.169)와는 연관성을 보이지 않았다.
결론: C. difficile 독소 효소면역검사는 C. difficile 감염 환자에서 질병의 증증도를 평가하는데 임상적으로 유용할 수 있으며, 특히 ATLAS 중증도 점수와 연관성이 높았다.
Methods: From December 2015 to May 2018, 91 patients suspected of suffering from antibiotic-related diarrhea among those who tested positive (including equivocal) in either fecal C. difficile toxin EIA (VIDAS toxin A/B enzyme-linked fluorescent assay, BioMerieux SA, France) or NAAT (Seeplex Diarrhea ACE kit, Seegene, Korea), or both were tested to investigate the correlation between the results of each assay and the severity of CDI via retrospective medical record review and statistical testing.
Results: For the 88 C. difficile tcdB NAAT positive cases, EIA positivity significantly correlated with the ATLAS score (P=0.005) but did not correlate with the CDAD severity (P=0.107) and CDSS scores (P=0.534). When EIA equivocal results were considered to be positive results, EIA positivity correlated with the CDAD severity (P=0.03) and ATLAS scores (P<0.001) but did not correlate with the CDSS score (P=0.169).
Conclusions: The C. difficile toxin EIA assay may be clinically useful in assessing the severity of disease in CDI patients, especially in correlation with ATLAS severity scores.
A rapid and accurate diagnosis is essential to guide treatment and prevent transmission . An effective diagnosis of CDI requires the presence of symptoms (typically diarrhea) and either a positive stool test for
Scoring systems composed of some potential factors for correlation with disease severity or treatment outcome have recently been developed and validated [6, 15-19]. We selected three scoring systems based on a combination of simple clinical and laboratory elements [17-19]. In this study, we aimed to investigate whether laboratory diagnostic methods using fecal
We reviewed the records of inpatients who had been tested with both the
1. Identification of
C. difficile toxin
Stool specimens were submitted to the clinical laboratory, where they were stored at 4°C and processed within 24 hours. Stool specimens were examined for toxins A and B by using a VIDAS toxin A/B enzyme-linked fluorescent assay (BioMerieux SA, France) according to the manufacturer’s instructions. The results were interpreted as positive (≥0.37), equivocal, or negative (<0.13), according to the intensity of fluorescence.
2. Identification of TcdB gene
3. CDI severity scoring systems
Three CDI severity scoring systems—the
Statistical analyses were performed using MedCalc for Windows, version 19.4 (MedCalc Software, Ostend, Belgium). The Chi-square test was used for comparison between two groups. The Mann-Whitney U test was used to correlate the combined results of toxin EIA and
1. Clinical and laboratory findings of CDI patients
Ninety-one patients were included as defined CDI cases in this study. The median age of the patients was 73 years (range: 29-87 years) and 56% were female. The clinical findings—including fever, admission to the ICU, history of systemic antibiotic treatment and presence of PMC—and laboratory findings—including WBC, CRP, serum albumin, eGFR, and serum creatinine—for five groups categorized according to the results of EIA and NAAT are summarized in Table 2. Among the 91 patients, 43 (48%) tested positive for both toxin EIA and
2. Correlation between results of toxin EIA and CDI severity scores
To determine the correlation between toxin EIA and CDI severity scores, we divided patients according to the toxin EIA results. Eighty-eight patients who were
The patients had a median CDAD severity score of 1.5 (range: 0-6), and 50.0% (44/88) of them were included in the mild group (scores 0 and 1). They had a median ATLAS score of 4 (range: 0-10), and 92.0% (81/88) of them were included in the mild group (scores 0-6). The patients had a median CDSS score of 1 (range: 0-3), and 83.0% (73/88) of them were included in the mild group (scores 0 and 1).
When toxin EIA equivocal results were included in the negative results, the toxin EIA and NAAT positive group showed significant correlation with the ATLAS score (
Figure 1. Correlation between the combined results of toxin EIA and
tcdBNAAT and three CDI severity scores. (A) Toxin EIA negative including equivocal results. (B) Toxin EIA positive including equivocal results. All data are median and interquartile ranges. Mann-Whitney U test, P-value < 0.05 was considered statistically significant.
C. difficileinfection; CDAD, C. difficileassociated diarrhea; CDSS, C. difficileseverity score; eq, equivocal. Acronym: ATLAS, age treatment leukocyte albumin serum creatinine.
In this study, three CDI severity scoring systems were used; CDAD, ATLAS, and CDSS scores [17-19]. Among them, the toxin EIA results best correlated with the ATLAS score and the positive EIA results including equivocal results correlated with the CDAD and ATLAS severity scores. Antimicrobial therapy remains the treatment of choice for CDI, and specific antimicrobial therapy guideline recommendations should be based on the severity of the disease . In a large, prospective, and randomized study by Zar et al. , the CDAD scoring system was developed based on clinical criteria for stratifying patients into mild and severe disease groups. Metronidazole and vancomycin were equally effective for the treatment of mild CDAD, but vancomycin was superior for treating patients with severe CDAD . The ATLAS scoring system composed of five simple and commonly available clinical and laboratory variables was suggested by Miller et al.  to predict response to therapy. This scheme highly correlates with the treatment outcome (R2=0.95;
The recently updated clinical guidelines for CDI by IDSA and SHEA recommend using a stool toxin assay as part of a multistep algorithm (i.e., GDH plus toxin; GDH plus toxin, arbitrated by NAAT; or NAAT plus toxin) rather than NAAT alone for all specimens received in the clinical laboratory when there are no pre-agreed upon institutional criteria for patient stool submission . The European Society of Clinical Microbiology and Infectious Diseases strongly recommends using a two-step algorithm for diagnosis of CDI instead of a single stand-alone assay . The algorithm should start with either the NAAT or GDH assay, and specimens testing positive in the first step should be tested further with the toxin A/B EIA .
We aimed to determine the correlation between the diagnostic methods for toxigenic
In this study, the correlation between EIA toxin positivity and CDI severity differed according to the scoring system, but it was best expressed by the ATLAS score. In addition, EIA toxin positivity, including equivocal results, was more closely related to the ATLAS and CDAD severity scores. The severity score in the CDAD and ATLAS scoring systems was higher for the EIA positive (including equivocal) group than for the EIA negative group. Therefore, the equivocal results of the EIA toxin assay may provide positive meaning for the risk stratification of CDI. In a recent study by Cohen et al. , the fecal
However, NAAT positivity seems less relevant to disease severity. In a large prospective study by Polage et al., the toxin immunoassay positive and PCR positive (Tox+/PCR+) patients had a longer duration of diarrhea than Tox−/PCR+ patients and Tox−/PCR− patients, but Tox−/PCR+ patients and Tox−/PCR− patients had a similar risk of diarrhea on most days . In a study by Kumar et al. , a positive
Our study has several limitations. We only evaluated the clinical and laboratory data at the time of CDI diagnosis by retrospective design and could not follow up on the clinical outcomes of the patients after treatment. Several factors can influence the severity and the clinical outcome of CDI, including the virulence of the infecting strain and the host immune responses ; however, these factors were not evaluated in this study. In addition, we could not perform the reference methods of the cell cytotoxicity assay or cytotoxigenic culture. Instead, we used the EIA and NAAT tests, which are readily available methods in routine laboratories.
In conclusion, the
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