국내 검사실에서의 대변 검경 검사에 대한 내부정도관리 현황
Internal Quality Assurance Status of Stool Examination as Assessed by a Questionnaire in Korean Clinical Laboratories
전남대학교 의과대학 진단검사의학교실
Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
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 2018; 8(1): 19-23
Published January 1, 2018
Copyright © The Korean Society for Laboratory Medicine.
This study aimed to survey the status of quality control (QC) assurance for stool examinations at clinical laboratories in Korea. We sent a questionnaire related to QC practices in stool examination by electronic mail to Korean clinical laboratories that performed stool examination. Overall, 20 of the 39 laboratories (51.3%) reported performing stool concentration methods, and 28 (71.8%) examined the slides using only saline. A large proportion (74.4%) of respondents did not check the internal QC because of the restriction of appropriate control materials. Only four laboratories (10.3%) checked the reactivity of the dye solution routinely. For appropriate external QC systems, QC slides (43.6%) were preferred, followed by QC materials (30.8%), virtual slides (17.9%), and a combination of the above options (7.7%). The most commonly observed parasites in stool samples at the clinical laboratories were Clonorchis sinensis (75%), followed by Endolimax nana, Enterobius vermicularis, and Entamoeba coli. The present study describes the difficulties in internal QC assessment due to the absence of standardized QC materials and systems. We hope the findings of this report will provide a foundation for a QC assessment program for stool examinations in the near future.
Diarrheal disease is a worldwide problem causing significant morbidity and mortality, especially in developing countries . It is common practice to request stool specimens for culture and/or parasitological examination in patients with diarrhea. Although it is common to think that parasitic diseases only occur in tropical regions, most of the intestinal infections occur in temperate regions of the world . In addition to common parasitic organisms, laboratories should identify some of the less common intestinal parasites often observed in individuals that have traveled abroad. In general, the diagnosis of parasites depends on microscopic identification; thus, it is crucial to maintain the inspection ability of each laboratory. Therefore, exact identification of intestinal parasites should be based on the quality control (QC) of microscopic examinations. The Clinical and Laboratory Standards Institute (CLSI) has established guidelines for stool examination re-garding collection, processing, and examination . However, data on the status of QC systems in clinical laboratories performing stool examinations are not sufficient . Thus, this study assessed the status of QC systems in Korean clinical laboratories performing stool examinations.
The study cohort consisted of clinical laboratories that perform stool examinations for parasitic infections within medical institutions (hospitals and medical centers) and in referral clinical laboratories accredited by the Korean Laboratory Accreditation Program . A brief questionnaire was sent by electronic mail to the directors and clinical pathologists in charge of the laboratories in order to survey the clinical laboratory practices related to stool examinations. The questionnaire included the use/method of stool concentration, use of additional stains, reactivity testing of the dye solution, and internal and external QC systems.
RESULTS AND DISCUSSION
In total, 39 clinical laboratories (24.2%, 39/161) responded to the survey. Most of the responses were from laboratories in medical institutions with 500–1,000 beds (53.8%, 21/39), followed by seven institutions with less than 200 beds (including three referral medical laboratories), seven institutions with 200–500 beds, and four institutions with greater than 1,000 beds (Table 1). Fecal concentration is recommended to increase the chance of detecting parasitic ova, cysts, and larvae, particularly in specimens where they are present in insufficient numbers to be seen using direct microscopy . Although more than a half of the laboratories (51.3%) performed stool concentration using formalin-ether or Tween 80, a third of the laboratories (30.8%) performed direct smears only. As the prevalence of intestinal parasitic infections in Korea decreases, fecal concentration should be used to increase sensitivity. Notably, more than 70% of responders (28 institutions) did not utilize additional stains, and there were no cases diagnosed as
The current study showed that the majority of laboratories (74.4%) did not perform internal QC testing for stool examinations. When asked why positive and negative control materials were not included before testing the patient samples, 75.9% of the laboratories indicated it was difficult to secure adequate positive and negative control materials. According to CLSI guidelines , stool samples used for QC can be fixed stool specimens that contain protozoa or polyvinyl alcohol (PVA)-preserved negative stool samples to which buffy coat cells have been added. The CLSI recommends that a QC slide should be included in each run of stained slides; however, this step is not mandatory, and the exact QC assessment can be adjusted at the laboratory’s discretion . A few laboratories (10.3%) checked the reactivity of the dye solution at least once every month. We found a gap between the laboratory protocols and the CLSI recommendation that fixative should be checked weekly or when using a new lot number . Only three laboratories compared the reactivity of the staining reagent lot by lot and included positive control materials. A QC smear prepared with a PVA-preserved stool or buffy coat cells should be used when a new stain is prepared or at least once every month according to CLSI guidelines . For external QC systems, the use of a QC slide (43.6%) was preferred, followed by QC materials (30.8%), virtual slides (17.9%), and a combination of the above options (7.7%). Generally, for external quality assessment programs, manufactured stool materials or slides have been used . Liebman et al. suggested that pooling pairs of stool specimens for microscopy is likely to be more cost effective than commercial QC slides . In order to obtain an adequate supply of pooling materials representing common and educationally important parasites, however, it might be necessary to survey endemic regions of parasitic disease around the world in addition to domestic multicenters. Moreover, the recently introduced Web Microscope for Parasitology could be an alternative tool .
In this study, 74.4% of respondents diagnosed protozoan infections without the aid of a special stain; however, 90.6% of respondents stated that special stains were necessary for the diagnosis of a protozoan infection. Furthermore, 81.1% of respondents indicated that additional enzyme-linked immunosorbent assays (ELISAs) could be necessary for the diagnoses of
The current study demonstrates that
Figure 1. The most commonly observed (A) and the second-most commonly observed (B) parasites during stool examinations in Korean clinical laboratories participating in this study.
To our knowledge, this is the first report to assess the current status of QC systems in Korean clinical laboratories performing stool examinations. We have found that many laboratories have inadequate internal QC systems, mostly due to limitations in obtaining appropriate positive control materials. This study highlights that it is crucial to support the development of adequate QC materials for the establishment of a QC system in the field of stool examination.
We thank the participating clinical laboratories for their valuable answers in this study. This study was supported by funding from the Laboratory Medicine Foundation (2016) and the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2016R1C1B1009746).
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