• BMB Reports
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• v.35 no.2
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• pp.248-250
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• 2002

Discrimination between the amplification of mRNA and contaminating genomic DNA is a common problem when performing a reverse transcriptase-polymerase chain reaction (RT-PCR). Even after treatment of the samples with DNAse, it is possible that negative controls (samples in which no reverse transcriptase was added) will give positive results. This indicates that there was amplification of DNA, which was not generated during the reverse transcriptase step. The possibility exists that Taq DNA polymerase acts as a reverse transcriptase, generating cDNA from RNA during the PCR step. In order to test this hypothesis, we incubated samples with a DNAse-free RNAse after the cDNA synthesis. Comparison of the results that were obtained from these samples (incubated with or without DNAse-free RNAse) confirms that the reverse transcriptase activity of Taq DNA polymerase I is a possible source of false positive results when performing RT-PCR from intronless genes. Moreover, we describe here a simple and rapid method to overcome the false positive results that originate by this activity of Taq polymerase.

• Annual Conference of KIPS
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• 2003.11c
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• pp.1843-1846
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• 2003

네트워크 기반의 공격 및 비정상 행위를 정확히 탐지하고 판단하기 위한 기존의 탐지 모델은 공격 룰셋의 패턴매칭 기반인 Misuse Detection System을 사용하고 있다. 그러나 이 시스템의 특성상 새로운 공격의 미탐지 및 공격 오인등으로 False Positive 가 높다는 단점이 있다. 본 논문은 전체 시스템의 성능을 판정하는 False Positve 에러율을 줄여 성능을 향상하기 위해 Meachine Learning기반의 Anomaly Detection System 을 결합한 새로운 탐지 모델을 제안하고자 한다. Anomaly Detection System 은 정상행위에 대한 비교적 높은 탐지율과 새로운 공격에 대한 탐지가 용이하다. 본 논문에서는 각 시스템의 탐지모델로 Snort 와 인스턴스 기반의 알고리즘인 IBL 을 사용했으며, 결합모델의 타당성을 검증하기 위해서 각 탐지 모델의 False Positive와 False Negative 에러율을 측정하였다.

• Tuberculosis and Respiratory Diseases
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• v.83 no.3
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• pp.211-217
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• 2020

The gold standard method for diagnosis of tuberculosis is the isolation of Mycobacterium tuberculosis through culture, but there is a probability of cross-contamination in simultaneous cultures of samples causing false-positives. This can result in delayed treatment of the underlying disease and drug side effects. In this paper, we reviewed studies on false-positive cultures of M. tuberculosis. Rate of occurrence, effective factors, and extent of false-positives were analyzed. Ways to identify and reduce the false-positives and management of them are critical for all laboratories. In most cases, false-positive is occurring in cases with only one positive culture but negative direct smear. The three most crucial factors in this regard are inappropriate technician function, contamination of reagents, and aerosol production. Thus, to reduce false-positives, good laboratory practice, as well as use of whole-genome sequencing or genotyping of all positive culture samples with a robust, extra pure method and rapid response, are essential for minimizing the rate of false-positives. Indeed, molecular approaches and epidemiological surveillance can provide a valuable tool besides culture to identify possible false positives.

• The Korean Journal of Cytopathology
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• v.10 no.1
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• pp.35-42
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• 1999

The accuracy of fine needle aspiration cytology(FNAC) of the lymph node was investigated through a review of 176 FNAC cases and the corresponding biopsies. We chose 157 FNAC cases after the exclusion of 19 inadequate ones. Sensitivity of malignancy was 94.0%, specificity 100%, false negativity 6.0%, and false positivity 0.0%. The overall diagnostic accuracy was 96.8%. Sensitivity of metastatic carcinoma was 98.0% and that of malignant lymphoma was 87.9%. False negative cases included one metastatic carcinoma and four malignant lymphomas. The aspirates of metastatic carcinoma with false negativity exhibited a diffuse smear of keratin debris without viable cells, which led to the difficulty in differentiation from benign epithelial cyst. The cases of malignant lymphoma with false negative diagnosis were two Hodgkin diseases, one Lennert's lymphoma, and one peripheral T cell lymphoma in the histologic sections. On the analysis of 39 cases of tuberculosis, 17 cases(43.6%) were diagnosed as tuberculosis, 4(10.3%) as granulomatous lymphadenitis, 3(7.7%) as necrotizing lymphadenitis, and 15(38.5%) as reactive hyperplasia or pyogenic inflammation. Sensitivity of tuberculosis was 53.9%. In conclusion, lymph node FNAC is an excellent non-invasive diagnostic tool for the diagnosis of metastatic carcinoma. The diagnostic accuracy of malignant lymphoma could be improved with flow cytometry or polymerase chain reaction for antigen receptor genes. For the FNAC diagnosis of tuberculosis, AFB stain, culture, and PCR would be helpful as adjuvant techniques.

• Korean Journal of Clinical Laboratory Science
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• v.45 no.4
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• pp.149-153
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• 2013

Candidiasis is a fungal infection of the most common causes; generally, opportunistic infections occur often in patients with weakened immune systems. Because of high rates in fungal infection patients and increasing frequency of being isolated from clinical materials, quickly identifying of Candida albicans is critical. By identifying 404 yeast cell strains of referred samples via API 20C kits, NGL and PRO tests and Germ tube (GT) test were conducted and compared. In the 3.0 McFarland yeast cells, 0.1% ${\rho}-nitrophenyl-N-acetyl-{\beta}-D-galactosaminide$ (NGL) and 0.04% ${\small{L}}$-proline ${\beta}$-naphtylamide (PRO) were each put in test tubes and incubated at $35^{\circ}C$ for 15, 30, 60 and 90 minutes. Afterwards, 1 drop of 2% NaOH was applied, and if the color turned yellow; it was positive for NGL test. Afterwards, 1% ${\rho}$-dimethylaminocinnamaldehyde was applied, and if the upper layer turned pink or red, it was positive for PRO test. NGL and PRO tests were conducted for all C. albicans and identified accurately within 30 minutes. In NGL, PRO test, false-positive, negative were not seen, whereas, GT test showed false-positive in 1 strain and false-negative in 3 strains. Therefore, sensitivity and specificity of NGL, PRO tests were 100% and 99.5%, respectively, and positive and negative predictive rate were 99.5% and 100%, respectively. However, GT test sensitivity and specificity were 98.5% and 99.5%, respectively, and positive and negative predictive rates were 99.5% and 98.5%, respectively. In conclusion, NGL, PRO tests are better than GT tests for sensitivity and specificity, therefore, these reliable tests will be useful in clinical laboratories.

• The Korean Journal of Cytopathology
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• v.8 no.2
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• pp.120-128
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• 1997

Fine needle aspiration cytology of breast lesion is well known as a simple, economic and effective diagnostic modality. For the evaluation of cytohistologic correlation, 256 cases of cytologic smears and subsequent histologic sections during 2-year period from Jan. 1995 to Dec. 1996 were reviewed. 1. Fifteen cases(5.9%) were proven as insufficient for evaluation, and 13 of them were fibrocystic change histologically. One case of carcinoma exhibiting sufficient amount of aspirates with no malignant cells on smear was regarded as inadequate. 2. Cytohistologic correlation of 240 cases revealed sensitivity 87.0%, specificity 100.0%, positive predictive value 100.0%, negative predictive value 97.0%, false positive rate 0.0% and false negative rate 13.0%. Total diagnostic accuracy is 95.7%. 3. Total 6 cases of negative were due to small amount of aspirates containing scantiness of malignant cells in two and underestimation in four. 4. Diagnostic concordance rates of fibrocystic change and fibroadenoma were 95.5% and 80.0%, respectively. Diagnostic discrepancies were noted in 7 cases of fibrocystic change and 6 cases of fibroadenoma, however, cytologic discrimination of two entities was not easy in seven of them. 5. In a case of phyllodes tumor and a case of duct ectasia, the discrepancy was due to targeting error. Other three cases(lymphoma, adenomyoepithelioma and granulomatous mastitis) were misinterpreted because of poor acquaintance with those entities. Diagnostic accuracy of fine needle aspiration cytology of breast lesions are relatively high. However, good technique on aspiration and adequate interpretation are necessary to reduce the false negative rate and the discrepancy between cytologic and histologic diagnoses.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.14
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• pp.5811-5814
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• 2014

Background: To investigate abnormal cervical histopathology (ACH) from hysterectomy specimens with normal preoperative Papanicolaou (Pap) smears. Materials and Methods: Medical records from May 2009 to April 2012 were retrospectively reviewed of subjects from whom hysterectomy specimens were taken in Thammasat University Hospital. All had normal preoperative Pap smears. ACH was the primary outcome. A p-value less than 0.05 was considered significant. A total of 483 subjects with an average age of 50.5 years were recruited. Benign cases of enlarged uterus and pelvic mass were present in 94% (430/483). Endometrial and ovarian cancer were found at 6.2 and 4.7%, respectively. In hysterectomy specimens there were 19 (4%) cases of ACH. Silent ACH with benign disease, endometrial and ovarian cancers were 1.2% (5/430), 33.3% (10/30) and 17.4% (4/23), respectively. The negative predictive value (NPV) and false negative rate of Pap smears were 96 and 4%, respectively. ACH in malignant cases were 27.9% (12/43) and 20% (2/10) in adequate (APS) and inadequate (IPS) Pap collection groups, respectively. ACH in benign condition were 0.68% (2/292) and 2.2% (3/138) in APS and IPS, respectively. ACH was more often found in hysterectomy specimens with indication of malignancy than benign conditions with statistical significance. One third of preoperative stage I endometrial cancer cases had cervical involvement. Conclusions: Silent ACH in normal preoperative Pap smear was 4 %. Inadequate Pap smear collection is still the major problem in this study. Reducing inadequate Pap smear collection could reduce the false negative rate.

• Journal of Preventive Medicine and Public Health
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• v.33 no.2
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• pp.226-230
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• 2000

Objectives : The purpose of this study was to suggest a proper method for the detection of heaptitis B surface antibody(anti-HBs) in a screening program for hepatitis B vaccination. Methods : Sensivitity, specificity and predictive values were compared between Immunochromatographic assay (ICA) and passive hemagglutination(PHA) in 978 subjects(565 males, 413 females, 19-78 years ranging in age, mean 46.5 years old). EIA was used as a standard method for the detection of HBsAb. Results : Sensitivity in the detection of anti-HBs of PHA and ICA was 88.7%, and 94.9%, specificity was 94.3% and 96.6%, negative predictive value was 96.5%, and 98.0%, and positive predictive value was 82.3%, and 91.3%,, respectively. False negative rate(11.3%) of PHA was higher than that(5.1%) of ICA. The higher the titer of anti-HBs in EIA was, the lower the false negative rate was. There was no false negative result in the cases with $101mIU/{\beta}c$ or more in EIA Conclusion : We suggest that ICA should be the choice of screening method in the detection of anti-HBs in Hepatitis B vaccination program.

• Korean Journal of Veterinary Research
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• v.38 no.3
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• pp.642-651
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• 1998

The accuracy of ultrasonography for determining the presence of a functional corpus luteum in subestrous dairy cows was investigated, using a radioimmunoassay for progesterone in plasma. Luteal status (high or low progesterone concentrations) was diagnosed in 534 cows, using B-mode transrectal ultrasonography. Accuracy of ultrasonography was 96.3% and 88.8% in the cows with and without functional corpus luteum, respectively. In 362 cows diagnosed with functional corpus luteum by ultrasonographic examination, 20 cows were diagnosed with the non-functional corpus luteum by analysis of plasma progesterone concentrations (false positive). In 172 cows with non-functional corpus luteum by ultrasonographic examination, 13 cows were diagnosed with the functional corpus luteum based on plasma progesterone assay (false negative). Most of the corpus luteum with well-defined border and homogeneous echotexture were diagnosed with functional corpus luteum. All cows that were not detected a corpus luteum by ultrasonographic examination were diagnosed as non-functional corpus luteum. The corpus luteum of cows that were diagnosed with false positive appeared homogeneous echotexture and above 15 mm in diameter, but the corpus luteum was the non-functional corpus luteum within Day 5 (Day 0 is ovulation day) or after Day 19. The corpus luteum of cows that were diagnosed with false negative appeared heterogeneous echogenicity and below 15 mm in diameter, but the corpus luteum was the functional corpus luteum after Day 5 or around Day 17. It was concluded that accuracy of ultrasonography was excellent for determining the presence of a functional corpus luteum in subestrous dairy cows. The corpus luteum that was diagnosed with false positive or false negative was the developing or regressing states. Thus, ultrasonography was required a serial examination of two or three times accurately diagnosing these corpus luteum.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.3
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• pp.959-963
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• 2015

Purpose: To find parameters that can increase alpha-fetoprotein (AFP) sensitivity and so help in accurate diagnosis and rapid management of hepatocullular carcinoma (HCC), as AFP has limited utility of distinguishing HCC from benign hepatic disorders for its high false-positive and false negative rates. Materials and Methods: Serum levels of AFP, 5'-nucleotidase enzyme activity (5-NU) and leucine aminopeptidase enzyme (LAP) activity were measured in 40 individuals. Results: LAP and 5'NU were elevated in HCC at p<0.001. Pearson correlation coefficients showed that changes in AFP exhibited positive correlation with both 5'-NU and LAP at (p<0.001). The complementary use of LAP only with AFP resulted in an increase in sensitivity of AFP from 75% to 90% in detecting HCC. The complementary use of both LAP and 5-NU with AFP resulted in an increased sensitivity of AFP in detecting HCC from 75% to 95%. Conclusions: LAP and 5-FU can be determined in HCC patients in combination with AFP to improve its sensitivity and decrease false negative results.