Performance Evaluation of MEDITAPE UC-11A Strip Test in Estimating the Urine Albumin-to-Creatinine Ratio and Urine Protein-to-Creatinine Ratio

30 mg/g), the concordance rate, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of UACR, analyzed using MEDITAPE UC-11A, were 80.5, 97.5, 67.0, 70.3, and 97.1%, respectively. Using UPCR, analyzed via quantitative assay, as a reference to estimate proteinuria (UPCR >0.15 g/g), the concordance rate, sensitivity, specificity, PPV, and NPV of UPCR, analyzed using MEDITAPE UC-11A, were 86.7, 94.4, 81.5, 77.6, and 95.6%, respectively.CONCLUSIONS: UACR and UPCR, analyzed using MEDITAPE UC-11A, exhibited relatively high sensitivity and NPV, which is beneficial for laboratory screening for both albuminuria and proteinuria.

Falsely Elevated Tacrolimus Concentrations Using Chemiluminescence Microparticle Immunoassay in Kidney Transplant Patient / 대한이식학회지

Tacrolimus is one of the effective immunosuppressive drugs used after an organ transplant procedure. However, due to its narrow therapeutic range, its usefulness in preventing transplant rejection and minimizing nephrotoxicity is dependent on the monitoring of whole blood trough levels of tacrolimus. A 49-year-old kidney transplant recipient presenting with cough and general weakness was admitted to the hospital. Due to the patient's deeply compromised clinical condition, an immunosuppressive therapy was discontinued. Tacrolimus concentrations in the patient's whole blood samples were measured, using an automated chemiluminescent microparticle immunoassay (CMIA) instrument. Interference was suspected because tacrolimus concentrations after the discontinuation of tacrolimus dose were 20.9 and 18.2 ng/mL at day 2 and 3, respectively. Tacrolimus concentrations were 11.1 and 12.6 ng/mL, respectively, when re-tested using an antibody-conjugated magnetic immunoassay (ACMIA). We evaluated the relationship between the CMIA and ACMIA results, and calculated the expected values from the regression equation. Residuals were –8.4 and –4 ng/mL, respectively. There have been several cases with false detection of elevated tacrolimus concentrations using ACMIA; however, such falsely detected elevations using CMIA have rarely been reported. When unexpectedly high concentrations of tacrolimus are detected by CMIA in transplant patients, an immediate re-test using another technique might be necessary to rule out falsely elevated results.

A Case of Hemolytic Transfusion Reaction Attributable to Anti-Jk(b) Abolished in the Enzyme Phase Reaction / 대한수혈학회지

We report a case of an intravascular hemolytic reaction attributable to anti-Jk(b) antibodies that were not detected using an enzyme phase antibody identification test. A 61-year-old male who had received two units of red blood cells was admitted to the emergency room because his urine was dark. LISS/Coombs gel column agglutination tests suggested the presence of anti-Jk(b) and anti-E antibodies. However, his serum was negative for the Jk(b) antigen when an enzyme phase test was performed. A positive reaction was evident, however, when EDTA-treated plasma was tested; this excluded any possible complement-mediated reaction. The patient was diagnosed with an intravascular hemolytic transfusion reaction, caused by anti-Jk(b), and was later discharged without specific complications after receiving antigen-negative blood transfusions.

Comparison of the Clinical Performance of Binax NOW RSV Versus Multiplex RT-PCR for Detection of Respiratory Syncytial Virus

BACKGROUND: Respiratory syncytial virus (RSV) is one of the most important causes of lower respiratory tract infection. The rapid antigen test is a simple, cheap, and quick method for RSV detection, however, it has an acknowledged low sensitivity. The aim of this study is to evaluate the diagnostic performance of the rapid antigen test by comparing it with a multiplex reverse transcription-PCR (RT-PCR). METHODS: A total of 557 nasopharyngeal aspirates or swabs that were submitted for both a rapid antigen test, Binax NOW RSV (Binax; Alere Scarborough, Inc., USA) and multiplex RT-PCR, Seeplex RV7 (Seegene Inc., Korea) were included in this study. We performed both tests according to the manufacturer's recommendations and analyzed the diagnostic performances of a rapid antigen tests based on the results of multiplex RT-PCR. RESULTS: Among the 557 specimens, the positive rates determined from the rapid antigen test and multiplex RT-PCR were 12.2% (N=68) and 25.1% (N=140), respectively. The relative sensitivity and specificity of the rapid antigen test were 46.4% and 99.3% based on the multiplex RT-PCR, respectively. Positive and negative predictive values were 95.6% and 84.7%, respectively. The diagnostic sensitivity was lower (28.6%) in children >36 months compared with children < or =36 months of age. Test sensitivity declined when RSV infection was accompanied by infection with other respiratory viruses. CONCLUSIONS: Binax NOW RSV exhibited good diagnostic performance, easy handling, and rapidity. However, it does have the possibility of false-negative results, and additional tests are needed when there is clinical suspicion of RSV infection.

Evaluation of the Automated Hematology Analyzer Sysmex XN-2000 and the Accuracy of Differential Leukocyte Counts Using the Low WBC Mode

BACKGROUND: The XN-series (Sysmex, Japan) is the new hematology analyzer from Sysmex, with new channels to improve the accuracy of differential leukocyte count and platelet count in the low cell count range. We evaluated the analytical performance and low white blood cell (WBC) mode of the XN-2000. METHODS: Precision, linearity, and carryover were evaluated for the analyzer. We analyzed the accordance of complete blood count (CBC), reticulocyte count, and differential leukocyte count between the XN-2000 and XE-2100 (Sysmex), using 200 samples from normal controls and patients. For 80 samples with a WBC count 0.9800 for all CBC parameters except mean corpuscular hemoglobin concentration, mean platelet volume, and platelet distribution width, and >0.9900 for differential leukocyte count except monocytes and basophils. The low WBC mode provided accurate counts for neutrophils and lymphocytes, with r>0.9300 for samples with a WBC count of 0.1-1.5x10(9) cells/L. CONCLUSIONS: The XN-2000 showed good analytical performance and correlation with the existing model, the XE-2100. The XN-2000 provided accurate results for differential leukocyte count in samples with a WBC count of 0.1-1.5x10(9) cells/L, and reduced manual slide reviews.

Postsurgical Wound Infection Caused by Mycobacterium conceptionense Identified by Sequencing of 16S rRNA, hsp65, and rpoB Genes in an Immunocompetent Patient / 대한임상미생물학회지

Rapidly growing mycobacteria are ubiquitous in the environment and are increasingly being recognized as opportunistic pathogens. Recently, a new species, Mycobacteium conceptionense, has been validated from the Mycobacterium fortuitum third biovariant complex by molecular analysis. However, there are few reports, and postsurgical wound infection by this species is rare. We report a case of postsurgical wound infection caused by M. conceptionense in an immunocompetent patient that was identified by a sequencing analysis of 16S rRNA, hps65, and rpoB genes.

A novel mutation of CACNA1A gene in episodic ataxia type 2 family in Korea

Episodic ataxia type 2 (EA-2) is a rare disorder presenting with paroxysmal vertigo and cerebellar dysfunction. EA-2 is known to be caused by mutations of the CACNA1A gene on chromosome 19q13. We examined a family of EA-2 with a novel mutation of the CACNA1A gene showing characteristic ocular symptoms. A-36-year woman visited our hospital with paroxysmal vertigo. When she experienced vertigo attack, she also suffered from gait disturbance, dysarthria, and ataxia. She complained that she could not ride in a car or a train that moved fast, because she could not visually follow the moving objects. Her mother, grandmother, and uncle also complained of similar symptoms. Video nystagmographic findings showed loss of optokinetic nystagmus. We found a novel missense mutation, R279C (c.835C>T), on exon 6 in the CACNAIA gene. This is the first report of a family with new mutation of EA-2 in Korea.

Clinical Significance of Clonal Rearrangement of the Immunoglobulin Gene in the Bone Marrow of Patients with B-cell Non-Hodgkin Lymphoma

BACKGROUND: In the early stages of non-Hodgkin lymphoma (NHL), it can be difficult to recognize minimal morphological changes in the bone marrow (BM). In particular, when the quality of the BM biopsy is poor, determining BM involvement is limited to microscopic findings on BM aspiration. In this study, we compared the results of clonal immunoglobulin (IG) gene rearrangements with BM morphology results in B-cell NHL patients who underwent BM analysis as a staging workup and evaluated the usefulness of the clonal IG gene rearrangements for staging. METHODS: Forty two B-cell NHL patients were analyzed. Clonal rearrangements of the IG heavy chain (IGH), kappa light chain (IGK) and lambda light chain (IGL) genes were detected using the IdentiClone(TM) Clonality assay (InVivoScribe Technologies, USA). Clinical characteristics and outcomes were evaluated based on the detection of monoclonal IG gene rearrangements. RESULTS: Monoclonal IG gene rearrangements were found in 9 of 42 patients (21.4%). Microscopic BM involvement was found in only 2 of 42 patients (4.8%). The monoclonality rate of IG genes in BM was correlated with clinical stage and the international prognostic index (P<0.01). Patients with monoclonal IG gene rearrangements in BM had a significantly higher relapse rate (P=0.014) and poorer overall survival at 2 yr (P<0.01). CONCLUSIONS: Clonality analysis of BM in B-cell NHL can contribute to identification of patients with occult BM involvement with a significantly poorer overall survival despite normal BM histology.

Autoimmune Hemolytic Anemia after Aplastic Crisis due to Parvovirus B19 Infection in a Patient with Hereditary Spherocytosis

Hereditary spherocytosis (HS) is a genetic disorder characterized by the production and destruction of spherocytes due to a deficiency of red cell membrane cytoskeletal proteins, resulting in the clinical presentation of chronic hemolytic anemia. This disease can be accompanied by an aplastic crisis due to parvovirus B19 infection. Parvovirus B19 infection causes diseases such as erythema infectiosum and arthritis, and can also trigger various autoimmune diseases, including autoimmune hemolytic anemia (AIHA). Here, we report a rare case of AIHA developing 3 months after an aplastic crisis due to parvovirus B19 infection in an 11-year-old boy with HS and provide the relevant literature review.

Autoimmune Hemolytic Anemia after Aplastic Crisis due to Parvovirus B19 Infection in a Patient with Hereditary Spherocytosis

Hereditary spherocytosis (HS) is a genetic disorder characterized by the production and destruction of spherocytes due to a deficiency of red cell membrane cytoskeletal proteins, resulting in the clinical presentation of chronic hemolytic anemia. This disease can be accompanied by an aplastic crisis due to parvovirus B19 infection. Parvovirus B19 infection causes diseases such as erythema infectiosum and arthritis, and can also trigger various autoimmune diseases, including autoimmune hemolytic anemia (AIHA). Here, we report a rare case of AIHA developing 3 months after an aplastic crisis due to parvovirus B19 infection in an 11-year-old boy with HS and provide the relevant literature review.

Detection of Anti-Lua in an Unexpected Antibody Screening Test: A Case Report and Literature Review / 대한수혈학회지

Lutheran a antigen (Lua) is detected in 6 to 8% of Caucasians and Africans. In Korean and other Asian populations, it is very rare or nearly absent. Therefore, although Lua has a considerable immunizing capacity, sensitization to Lua is a rare event. Here we report on a rare case of anti-Lua in a 70 year-old female patient with Lu (a-/b+) phenotype and review the relevant literature. Due to the paucity of Lua positive panel cells in antibody screening and identification tests, detection of this rare antibody to Lua antigen is not feasible. Therefore, we should keep in mind the possibility of the misleading false negative result in detection of antibody to this low incidence antigen.

Three-way Translocation of MLL/MLLT3, t(1;9;11)(p34.2;p22;q23), in a Pediatric Case of Acute Myeloid Leukemia / 대한진단검사의학회지

The chromosome band 11q23 is a common target region of chromosomal translocation in different types of leukemia, including infantile leukemia and therapy-related leukemia. The target gene at 11q23, MLL, is disrupted by the translocation and becomes fused to various translocation partners. We report a case of AML with a rare 3-way translocation involving chromosomes 1, 9, and 11: t(1;9;11)(p34.2;p22;q23). A 3-yr-old Korean girl presented with a 5-day history of fever. A diagnosis of AML was made on the basis of the morphological evaluation and immunophenotyping of bone marrow specimens. Flow cytometric immunophenotyping showed blasts positive for myeloid lineage markers and aberrant CD19 expression. Karyotypic analysis showed 46,XX,t(1;9;11)(p34.2;p22;q23) in 19 of the 20 cells analyzed. This abnormality was involved in MLL/MLLT3 rearrangement, which was confirmed by qualitative multiplex reverse transcription-PCR and interphase FISH. She achieved morphological and cytogenetic remission after 1 month of chemotherapy and remained event-free for 6 months. Four cases of t(1;9;11)(v;p22;q23) have been reported previously in a series that included cases with other 11q23 abnormalities, making it difficult to determine the distinctive clinical features associated with this abnormality. To our knowledge, this is the first description of t(1;9;11) with clinical and laboratory data, including the data for the involved genes, MLL/MLLT3.

Prognostic Significance of TEL/AML1 Rearrangement and Its Additional Genetic Changes in Korean Childhood Precursor B-Acute Lymphoblastic Leukemia / 대한진단검사의학회지

BACKGROUND: TEL (ETV6)/AML1 (RUNX1) rearrangement is observed in approximately 20-25% of childhood precursor B-ALL and is associated with a favorable outcome. Additional genetic changes, associated with TEL/AML1, are frequently found. We evaluated the prevalence and prognostic significance of TEL/AML1 rearrangement and additional genetic changes in the TEL and AML1 genes in Korean childhood precursor B-ALL. METHODS: We performed FISH using LSITEL/AML1 ES probe (Vysis, USA) in 123 children diagnosed as having precursor B-ALL and assessed clinical relevance of the TEL/AML1 rearrangement and additional genetic abnormalities. RESULTS: The frequency of TEL/AML1 was 17.1% (21/123) in patients with precursor B-ALL. TEL/ AML1-positive group showed male predominance (P=0.012) and younger age of onset than TEL/ AML1-negative group by 1.6 yr (P=0.013). The outcome of TEL/AML1-positive group tended to show lower incidences of relapse (1/21 vs 20/102), death (1/21 vs 17/102) and longer event free survival. Among TEL/AML1-positive patients, unrearranged TEL deletion, AML1 gain, and unrearranged TEL deletion combined with AML1 gain were detected in 61.9%, 23.8%, and 9.5%, respectively. There were no significant differences in the clinical features and outcome according to the presence or absence of additional genetic changes. CONCLUSIONS: The frequency of TEL/AML1 and additional genetic changes in TEL and AML1 is higher than previous studies in Korean children, and in close agreement with usually reported one, 20-25%. TEL/AML1-positive group showed a tendency toward better prognosis. Further study is needed to clarify the prognostic significance of additional changes in TEL and AML1 based on a large sample size.

Identification of a Novel Deletion Region in 3q29 Microdeletion Syndrome by Oligonucleotide Array Comparative Genomic Hybridization / 대한진단검사의학회지

BACKGROUND: The 3q29 microdeletion syndrome is a genomic disorder characterized by mental retardation, developmental delay, microcephaly, and slight facial dysmorphism. In most cases, the microdeletion spans a 1.6-Mb region between low-copy repeats (LCRs). We identified a novel 4.0- Mb deletion using oligonucleotide array comparative genomic hybridization (array CGH) in monozygotic twin sisters. METHODS: G-banded chromosome analysis was performed in the twins and their parents. Highresolution oligonucleotide array CGH was performed using the human whole genome 244K CGH microarray (Agilent Technologies, USA) followed by validation using FISH, and the obtained results were analyzed using the genome database resources. RESULTS: G-banding revealed that the twins had de novo 46,XX,del(3)(q29) karyotype. Array CGH showed a 4.0-Mb interstitial deletion on 3q29, which contained 39 genes and no breakpoints flanked by LCRs. In addition to the typical characteristics of the 3q29 microdeletion syndrome, the twins had attention deficit-hyperactivity disorder, strabismus, congenital heart defect, and gray hair. Besides the p21-activated protein kinase (PAK2) and discs large homolog 1 (DLG1) genes, which are known to play a critical role in mental retardation, the hairy and enhancer of split 1 (HES1) and antigen p97 (melanoma associated; MFI2) genes might be possible candidate genes associated with strabismus, congenital heart defect, and gray hair. CONCLUSIONS: The novel 4.0-Mb 3q29 microdeletion found in the twins suggested the occurrence of genomic rearrangement mediated by mechanisms other than nonallelic homologous recombination. Molecular genetic and functional studies are required to elucidate the contribution of each gene to a specific phenotype.

Factors Affecting the Difference between the Low-Density Lipoprotein Cholesterol Concentrations Measured Directly and Calculated Using the Friedewald Formula / 임상검사와정도관리

BACKGROUND: National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) is the guideline for detection evaluation, and treatment of high blood cholesterol in adults. The risk of coronary heart disease (CHD) is assessed by the presence of CHD risk equivalents and the number of risk factors. LDL-cholesterol is the goal of treatment for hyperlipidemia. Contents: The most common approach for determining LDL-cholesterol level in clinical laboratory is to calculate it based on Friedewald formula. For accurate risk assessment by the calculated LDL-cholesterol, good analytical performances of total cholesterol, HDL-cholesterol and triglyceride are prerequisite. Even if the analytical performance of these three analytes are within the acceptable criteria, pooled imprecision and bias of the calculated LDL-cholesterol could not meet the criteria for LDL-cholesterol. Even under conditions satisfying the requirements of Friedewald formula, the calculated LDL-cholesterol level was lower than the directly measured level and the difference was dependent on the level of triglyceride, LDL-cholesterol and total cholesterol. When evaluatingpatients with hyperlipidemia, Friedewald calculation may underestimate the risk for coronary heart disease which may lead to inappropriate treatment option. CONCLUSIONS: When evaluating patients with hyperlipidemia, direct measurement of LDL-cholesterol appears to be better than Friedewald calculation.

Relationship between In Vitro Chemosensitivity assessed with MTT Assay and Clinical Outcomes in 103 Patients with Acute Leukemia / 대한진단검사의학회지

BACKGROUND: Cellular drug resistance is supposed to play a major role in chemotherapy failure or relapse. The purpose of this study was to analyze the relationship between in vitro chemosensitivity test results using a 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and clinical response on chemotherapy, and to find the possibility of optimizing the treatment protocol for individual patients according to their actual drug resistance. METHODS: For MTT assay, we obtained bone marrow aspirates from 103 patients with acute leukemia at the time of initial diagnosis or relapse. The following drugs were tested: cytarabine, vincristine, methotrexate, daunorubicin, dexamethasone, L-asparaginase, and mitoxantrone. To evaluate clinical responses after induction chemotherapy, we followed up on their bone marrow study. RESULTS: In our study, in vitro chemosensitivity test with the MTT assay significantly predicted whether patients with AML remained continuous complete remission or went into relapse. It also predicted whether or not child patients with ALL would acquire complete remission after induction chemotherapy. CONCLUSIONS: Although it does not provide the insight into the mechanisms that cause drug resistance, the MTT assay may be a useful tool in individually optimizing the chemotherapy of patients with acute leukemia.

Meta-analysis of the Association between HLA-DRB1 Allele and Rheumatoid Arthritis Susceptibility in Asian Populations

The aims of this study were to summarize results on the association of HLA-DRB1 with rheumatoid arthritis (RA) in Asians and to determine if the shared epitope (SE) hypothesis could explain the meta-analysis results. Among the papers published between January 1987 and July 2006 on RA susceptibility in Asian-Mongoloid populations (Korean, Japanese, Chinese, and Thai), 12 were selected for the metaanalysis. Mongoloid-Asian patients with RA had significantly higher frequencies of HLA-DRB1*0101, *0401, *0410, and *1001 than controls (OR 1.5-2.1, p<0.05 for association). When analyses were restricted to more ethnically homogeneous populations, HLA-DRB1*0405 showed a significant susceptibility to RA in Koreans (OR 5.65, 95% CI 4.32-7.39), whereas the HLA-DRB1*0301, *0403, *0406, *0701, *1301, and *1405 alleles showed protective association with RA (OR 0.32-0.70, p<0.05 for association). In conclusion, it was found that HLA-DRB1 *0101, *0401, *0405, *0410, and *1001 are susceptible, while HLA-DRB1* 0301, *0403, *0406, *0701, *1301, and *1405 are protective in Asian-Mongoloids. All the RA-associated alleles except DRB1*0301 could be explained by the structural model supporting the SE hypothesis that RA susceptibility is determined by the combination of amino acid residues at HLA-DR beta71 and beta74, not by beta71 alone.

A Case of Beauveria bassiana Keratitis / 대한임상미생물학회지

Beauveria bassiana is a hyaline Hypomycetes, which is known as an insect pathogen causing infections in silkworm. It is a rare opportunistic pathogen of human accounted for pulmonary infection, keratitis, and deep tissue infection. We report the first case of B. bassiana keratitis in Korea. A 64-year-old man with a 10-year history of herpetic keratitis was referred for the treatment of infectious keratitis in the right eye. Corneal scrapings showed septate hyaline hyphae on calcoflour white-KOH preparation and their cultures grew B. bassiana. At the beginning, the patient was treated empirically with an antiviral and antibiotics, and then the treatment was changed with antifungal agents including voriconazole, when the culture results were available. Since the inflammation had been aggravated despite medical treatments, he underwent a penetrating keratoplasty (PKP). The excised button of cornea showed the hyphae. The treatment with voriconazole was continued until 2 months after PKP, and fungal keratitis did not relapse during a 6-month follow-up period.

Evaluation of the Phoenix System for the Detection of Methicillin-Resistent Staphylococcus aureus / 대한임상미생물학회지

BACKGROUND: We evaluated the BD Phoenix Automated Microbiology System (Phoenix) for its ability to detect methicillin resistant Staphylococcus aureus (MRSA) and compared the results to those obtained by the Clinical and Laboratory Standards Institute (CLSI) agar dilution method, a mecA gene PCR method, and the MicroScan WalkAway 96 System (MicroScan). METHODS: One hundred seventy S. aureus strains (Group I) isolated from blood and urine cultures were collected from eight university hospitals and 58 strains (Group II) including 20 blood isolates among Group I and 38 isolates from skin lesions of atopic patients were collected from Asan Medical Center. All 208 isolates were tested with Phoenix using PMIC/ID-53 panels, and the tests were repeated when the results were indeterminate. The results by Phoenix were compared to the susceptibility results obtained by reference methods: the CLSI method for oxacillin MIC for Group I strains, and a PCR assay method for detection of the mecA gene and MicroScan tests for oxacillin susceptibility for Group II strains. RESULTS: One hundred strains (58.8%) in Group I were MRSA and 28 strains (48.3%) were mecA positive in Group II. Compared to the CLSI method, Phoenix showed the sensitivity and specificity of 100% and MIC agreement of 99.4% for Group I strains. The level of agreement between Phoenix and MicroScan for oxacillin MIC and their interpretation were 98.3% and 100%, respectively, for Group II strains. Both MicroScan and Phenix failed to detect one mecA-positive strain: its MIC was shown as 2 microgram/mL twice by MicroScan and 2 microgram/mL twice and > 2 microgram/mL once by Phoenix. The frequency of the indeterminate results was 5.5% and the mean time to completion of the tests was 12.8 (10.2-16) hours in Phoenix. CONCLUSION: Phoenix showed a high level of sensitivity and specificity for the detection of MRSA with an excellent correlation with MicroScan. Further evaluation is required for detection of heterogeneous MRSA.

Clinical Significance of Low-colony Count Scotochromogen Nontuberculous Mycobacteria / 결핵및호흡기질환

BACKGROUND: Even though it has been suggested that low-colony, scotochromogen nontuberculous mycobacteria (NTM) are usually contaminants and not true pathogens, evidence for this hypothesis has not been provided. This study investigated the colony characteristics, organism identification, and clinical significance of low-colony scotochromogen. METHODS: The laboratory cultured 6,898 respiratory clinical specimens for an examination of mycobacteria over a three-month period. A low-colony count was arbitrarily defined as < or = 20 colonies. This study analyzed the recovery rate of the mycobacteria, the number of colonies and their gross characteristics, and their clinical significance. PCR- restriction fragment length polymorphism analysis was carried out to identify the NTM species. NTM pulmonary disease was defined according to the American Thoracic Society. RESULTS: A total of 6,898 respiratory specimens for mycobacterium were cultured. Of these, 263 (3.8%) grew NTM, and 382 (5.5%) grew M. tuberculosis. Of the 263 cultured NTM specimens, 124 (47.1%) were scotochromogens. The smear-positive rate was significantly lower in these scotochromogens (4.8%) than in the non-scotochromogens (23.7%) (p<0.05). The most common isolates were M. gordonae (83/102, 81.4%) in the scotochromogens, and MAC (52/121, 43.0%) in the non-scotochromogens. Even though three out of 113 patients with a low-colony scotochromogen has been diagnosed with NTM pulmonary disease, the isolated scotochromogen was not considered to be the cause of the NTM disease but was just a contaminant. CONCLUSION: In this study, the most common isolate of a low-colony count scotochromogen was M. gordonae, which appeared to be contaminants and not true pathogens. Greater efforts in the quality control of a mycobacterium laboratory are needed in cases where there is a high recovery rate of low-colony count scotochromogen.