Evaluation of the Vacuum Blood Collection Tube, V-Tube, a Domestic Product for Clinical Chemistry and Thyroid Hormone Assays

BACKGROUND: It is known that the blood collection tube used can cause fluctuations in laboratory test results. We compared test results obtained when blood was collected in V-tube (AB Medical, Korea), BD Vacutainer Tubes (BD, USA), and Greiner Vacuette Tubes (Greiner, USA) in clinical chemistry and thyroid hormone assays. METHODS: One hundred volunteers from three hospitals were recruited and the peripheral blood samples were collected in each of the three serum separation tubes (SSTs). These samples were used for 28 routine clinical chemistry assays and three thyroid hormone assays. The results were analyzed by the Student paired t-test and the Bland-Altman plot. For stability tests, the initial results were compared with the day 1 (24±2 hours), day 3 (72±2 hours), and day 7 (168±2 hours) results, respectively. RESULTS: The difference in the test results obtained from the samples in each tube (V-Tube vs. BD-Tube, V-Tube vs. Greiner-Tube, and BD-Tube vs. Greiner-Tube) were satisfied with the Clinical Laboratory Improvement Amendments of 1988 allowable difference ranges. Except for four analytes (low-density lipoprotein cholesterol, magnesium, potassium, and thyroid-stimulating hormone), all analytes were within the allowable critical difference range based on biological variability. The paired t-test revealed significant differences between the results of nine assays for samples in V-Tube vs. BD-Tube and seven assays for samples in V-Tube vs. Greiner-Tube, but each set of results showed good correlations. The test results on different days showed a significant difference in several assays, but they were within the allowable difference range. CONCLUSIONS: The assay results for blood samples collected in SST V-Tubes were comparable to those obtained when blood was collected in BD Tubes and Greiner Tubes, and the blood collected in V-Tubes also showed excellent results in the stability tests.

Aminoglycoside Susceptibility Profiles of Enterobacter cloacae Isolates Harboring the aac(6')-Ib Gene / 대한진단검사의학회지

The aminoglycoside 6'-N-acetyltransferases of type Ib (aac(6')-Ib) gene confers resistance to amikacin, tobramycin, kanamycin, and netilmicin but not gentamicin. However, some isolates harboring this gene show reduced susceptibility to amikacin. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommends a revision of the phenotypic description for isolates harboring the aac(6')-Ib gene. In this study, we determined the aminoglycoside susceptibility profiles of 58 AAC(6')-Ib-producing Enterobacter cloacae isolates. On the basis of the CLSI and EUCAST breakpoints, a large proportion (84.5% and 55.2%, respectively) of these 58 isolates were found to be susceptible to amikacin. However, among the isolates that were shown to be anikacin-susceptible according to the CLSI and EUCAST breakpoints, only 30.6% and 18.8% isolates, respectively, could be considered to have intermediate resistance on the basis of the EUCAST expert rules. Further studies should be conducted to determine the aminoglycoside susceptibility profiles of aac(6')-Ib-harboring isolates from various geographic regions and to monitor the therapeutic efficacy of amikacin in infections caused by these isolates.

The Comparison of Parathyroid Hormone Degradation Effect by Various Protease Inhibitors in Blood Specimen / 대한진단검사의학회지

BACKGROUND: The objective of this study was to evaluate the role of proteases on the degradation of parathyroid hormone (PTH) in blood samples. METHODS: Protease inhibitors with specificity against serine proteases (aprotinin), cysteine proteases (E-64), serine and cysteine proteases (leupeptin), metalloproteases (EDTA), or a protease inhibitor cocktail with a broad spectrum of inhibitory activity were added to blood samples. After storage at room temperature (0-48 hr), PTH levels were measured. RESULTS: PTH levels in samples with the protease inhibitor cocktail did not change significantly after 48 hr of storage at room temperature, but the average PTH levels decreased by 40.7% and 20.1%, in samples stored at room temperature and stored at 4degrees C without protease inhibitors, respectively. PTH levels in samples with leupeptin were stable for up to 24 hr. After 48 hr, the mean PTH levels decreased by 17.1%, 16.0%, 26.2%, and 32.1%, with 500 KIU/mL aprotinin, 100 micro mol/L leupeptin, 10 micro mol/L E-64, and 10 micro mol/L EDTA, respectively, in the samples stored at room temperature. CONCLUSIONS: The decrease in PTH levels in blood samples seemed to be due to the degradation of PTH by proteases. Various proteases, including especially serine proteases, would act together to degrade PTH in blood specimen. The PTH degradation may be inhibited in blood specimen with protease inhibitor cocktail.

Performance Characteristics of Glycated Albumin and Its Clinical Usefulness in Diabetic Patients on Hemodialysis / 대한진단검사의학회지

BACKGROUND: The HbA1c has been considered to underestimate glucose level in diabetic patients on hemodialysis, therefore, glycated albumin (GA) was recently introduced to assess the glycemic control for those cases. We evaluated the performance of GA assay kit of Lucica GA-L (Asahi Kasei Pharma Co., Japan) and compare it with HbA1c for estimating glucose levels. METHODS: Tests for precision, linearity and interference were performed and reference interval was determined. Thirty eight of non-hemodialysis and seventy of hemodialysis patients were recruited, whose glucose levels of three-, two- and one-month prior to this study were available for calculating weighted means of glucose (WMGs). The correlation coefficients and the slopes of regression equation between WMG and HbA1c or GA were compared between two groups. Multiple linear regression analyses were used to determine significant predictor for HbA1c and GA. RESULTS: Total CV was 2.2% at concentration of 13.7% and 2.8% at 24.6%. The dilution curve between 15.7% and 62.1% was linear. Reference intervals were 10.0% to 16.5% for male and 11.4% to 17.6% for female. The correlation coefficients between WMG and GA were 0.682-0.713 in hemodialysis and 0.640-0.677 in non-hemodialysis. Those between WMG and HbA1c were 0.568-0.625 in hemodialysis and 0.735-0.783 in non-hemodialysis. The slopes of regression equation between GA and WMG in hemodialysis were 0.080-0.090 and 0.130-0.147 in non-hemodialysis. Those between HbA1c and WMG in hemodialysis were 0.012-0.014 and 0.029-0.032 in non-hemodialysis. GA was not influenced by hemodialysis status while HbA1c was. CONCLUSIONS: The claimed performance characteristic of Lucica GA-L were verified. WMG were better reflected by GA rather than HbA1c in patients on hemodialysis.

Comparison of Quantitative Results among Two Automated Rapid Plasma Reagin (RPR) Assays and a Manual RPR Test / 대한진단검사의학회지

BACKGROUND: We compared two automated Rapid Plasma Reagin (RPR) assay kits with a manual RPR assay kit to evaluate the possibility of using the two automated RPR assays as an alternative to the manual RPR assay for a quantitative monitoring. METHODS: One hundred eighty-five samples were analyzed, including 16 sera from patients with primary, secondary, and latent syphilis. Measured RPR unit (R.U.) values of two automated RPR assay kits, Mediace RPR (Sekisui Chemical Co., Ltd, Japan) and HBi Auto RPR (HBI Co., Ltd, Korea), were compared with the RPR titers of Macro-Vue RPR card test (Becton Dickinson BD Microbiology systems, USA). As a confirmatory test, Anti-Treponema pallidum EUROLINE WB (IgG) and Anti-Treponema pallidum EUROLINE WB (IgM) (Euroimmun, Germany) were used. RESULTS: There was a prozone effect with Mediace RPR at RPR titer (card test) of 1:16, but not with HBi Auto RPR. The R.U. values of the two automated RPR assays did not show proportional increase to the RPR titer. Agreement between manual RPR and two automated RPR assay kits, Mediace RPR assay and HBi Auto RPR assay, were 83.8% and 83.2%, respectively. CONCLUSIONS: The two automated RPR assay kits could not be used as an alternative to manual RPR test for quantitative analysis of RPR titer. As Mediace RPR shows a prozone effect at relatively low RPR titer, caution is needed in the interpretation of the measured values.

Comparison of Two Plastic Vacuum Tubes and Glass Tube for Use in Thyroid Hormone Tests / 임상검사와정도관리

BACKGROUND: Plastic tubes have recently been used for blood collection tubes in clinical laboratories. The silicone coated plastic tube is said to be very similar with the glass tube and to show no difference with the glass tube in routine blood test except for some tests such as hormone tests and drug monitoring. So, we investigated the influence of plastic tube on the thyroid hormone test using two types of plastic vacuum tubes. METHODS: A total of 105 cases for the total triiodothyronine (T3), total thyroxine (T4), and thyroid stimulating hormone (TSH) were studied. The glass tube was a plain glass tube, and the plastic tube was a serum separator tube with gel. The plastic vacuum tubes used in this study were the SST II plus tube (Becton Dickinson, Franklin Lakes, USA) and the Vacuette tube (Greiner Bio-One, Kremsmunster, Austria). An IMMULITE 2000 analyzer (Diagnostic Products Corporation, Los Angeles, USA) was used to measure the total T3, total T4 and TSH. RESULTS: Comparisons of the measured values within 1 hour of blood collection in the plastic tube with that in the glass tube are as follows. There was no difference between the Vacuette tube and the glass tube for the three tests, while there was statistically significant difference between the SST II plus tube and the glass tube for the total T3 and total T4. CONCLUSIONS: It might need more cautious interpretation of the results by a solid-phase, competitive chemiluminescent enzyme immunoassay, when the plastic vacuum tube is used as a blood collection tube instead of the glass tube.

Evaluation of BD Lab Reagents for Chemistry Analyzers / 임상검사와정도관리

BACKGROUND: Many modern chemistry analyzers are open systems and they can use reagents other than those supplied by the manufacturer of the analyzer. There are many generic reagents for use in open systems. The objective of this study was to evaluate the analytical performance of the BD Lab reagents (BD Lab co., Korea) which were generic reagents. METHODS: Sixteen kinds of reagents of total protein, albumin, blood urea nitrogen (BUN), creatinine, glucose, uric acid, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin, alkaline phosphatase (ALP), lactate dehydrogenase (LD), gamma glutamyl transferase (GGT), calcium, inorganic phosphorus, total cholesterol, triglycerides were tested for precision, linearity and correlation according to the NCCLS guidelines (EP5-A, EP6-A, EP9-A2). Toshiba 200-FR Neo (Toshiba Medical Systems Co., Japan) was used in this evaluation. RESULTS: All reagents showed acceptable precision with total coefficients of variation less than 7%. Comparison of BD Lab reagents with the current reagents by regression analysis resulted in slopes ranging from 0.86 to 1.06 and correlation coefficients more than 0.975. Fifteen of sixteen reagents showed good linearity in broad range. CONCLUSIONS: BD Lab reagents showed good precision, linearity, and correlation. Therefore, we conclude that the BD Lab reagents can be an alternative of currently used reagents in chemistry analyzers.

Typing and Antimicrobial Susceptibilities of Methicillin Resistant Staphylococcus aureus (MRSA) Strains Isolated in a Hospital in Korea

Methicillin-resistant Staphylococcus aureus (MRSA) strains may cause serious nosocomial infections, including pneumonia and septicemia. The rate of methicillin-resistance among S. aureus isolates in Korea is over 50%. In this study, 90 MRSA isolates from Kyung Hee University Hospital were characterized employing bacteriophage typing, pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing. Eighty percent of the strains could be phage-typed. The largest group or 40% of the strains belonged to lyso group III, followed by 32% of the isolates which produced a reaction with regional additional phages. Phage type 83A was most frequently encountered, followed by phage type D11. PFGE patterns confirmed the presence of two major clusters, which comprise the isolates belonging to lyso group III and the strains that were typable with regional additional phages. The latter group also contained a number of strains that were nontypable with bacteriophages. The resistance rates to ciprofloxacin, erythromycin, tetracycline, gentamicin and clindamycin were over 94%. Strains with intermediate resistance to vancomycin strains or resistance to mupirocin were not found. In conclusion, this study demonstrates that the results of phage typing are confirmed and supplemented by PFGE data.

Comparison of the MGIT (Mycobacteria Growth Indicator Tube) with Ogawa media for recovery of Mycobacteria / 대한임상미생물학회지

BACKGROUND: It takes long time to cultivate Mycobacterium tuberculosis on solid media from clinical specimens. Although there is progress in the detection of tuberculosis using liquid media, Ogawa media is broadly used in Korea. In the 1990s, the BACTEC 460 system (Becton Dickinson, Sparks, MD, USA) was used in some laboratories in Korea, but at present, it is not used because of the accumulation of radioactive waste and the risk of cross-contamination. The BACTEC MGIT 960 system (Becton Dickinson, Sparks, MD, USA) is one of the new systems using liquid media. MGIT system uses oxygen-quenching fluorescence sensor technology instead of radioactive material. We evaluated MGIT for the sensitivity and specificity for the diagnosis of Mycobacterium tuberculosis by comparison with Ogawa media. METHODS: A total of 232 sputum specimens were collected from patients admitted to the hospital. All specimens were processed by 4% NaOH and 0.5% NALC. After inoculation of MGIT with 0.5 mL and Ogawa with 0.3 mL of the processed specimen, the media were observed every 3 days until 6 weeks and 8 weeks, respectively. RESULTS: A total of 99 isolates of mycobacteria were recovered from 232 specimens. Ninety nine isolates were detected with MGIT, as contrasted with 64 detected with Ogawa media. The mean times to detection of the Mycobacterium species were 12.6 days for MGIT, 23.7 days for Ogawa media. Contamination rates were 5.1% for MGIT, 5.6% for Ogawa media. CONCLUSION: From our study, we conclude that MGIT is a superior method for recovery rate and time to detection of Mycobacteria to Ogawa media.

Comparative evaluation of fluconazole susceptibility methods for Candida species: Broth microdilution test, E test and disk diffusion test / 대한임상병리학회지

BACKGROUND: Currently fungal infections have been increasing in clinical aspect. Among them Candida albicans is considered as the most pathogenic. National Committee for Clinical Laboratory Standards(NCCLS) recommends broth macrodilution method for antifungal susceptibility test, but it is difficult to perform. E test is a relatively easy method to perform for the susceptibility testing. So in this study, antifungal susceptibility procedures were compared to determine MIC for fluconazole against 130 Candida strains isolated from clinical specimens. METHOD: The tests including were microdilution method, E test and disk diffusion method. The latter two tests were performed in casitone agar and the former test performed in RPMI 1640 media(Sigma Chemical co. St. Louis, USA). MIC was determined after 24 hrs of incubation. We used Candida albicans ATCC 90018 and Candida parapsilosis ATCC 90028 as controls. A total of 130 strains(93 C. albicans, 29 C. tropicalis, 5 C. parapsilosis and 3 C. glabrata) were tested. RESULTS: The MIC50 and MIC90 of broth microdilution test for C. albicans was > OR =64 microgram/mL equivalently. Agreement of > OR = +/-2 dilution between broth microdilution test and E test was 54 %, and the concordance rate was 55%. The concordance rate between E test and disk diffusion was 90%. CONCLUSIONS: From this study, we conclude that E test can be used as a alternative and convenient method to macrodilution method to determine MIC of fluconazole. But it is necessary for attention to microcolonies surrounding the E test strip. Disk diffusion method is rapid and also can be used as an alternative and convenient method.

Evaluation for usefulness of bone marrow study in fever of unknown origin / 대한임상병리학회지

BACKGROUND: As the new diagnostic methods for evaluation of fever of unknown origin (FUO) have been developed, the clinical spectrum of FUO has been changed. Although bone marrow study was commonly used in the evaluation of FUO, it's value has not been established. We evaluated the value of bone marrow study for FUO patients. MATERIAL AND METHODS: The 53 patients with FUO who have been performed bone marrow study from 1991 to 1998 were studied, retrospectively. Radiologic, serologic, hematologic, biopsy of tissue, chemistry, molecular and microbiologic review were included in this study. RESULTS: The etiology of FUO was identified in 31(58.5%) of the 53 patients through bone marrow examination. Of 53 patients, bacterial infection accounts for 12(22.6%); neoplasm 10(18.9%); SLE 3(5.7%); aplastic anemia 2(3.8%); drug induced 2(3.8%); necrotizing lymphadenitis 1(1.8%); hereditary spherocytosis 1(1.8%). Bone marrow examination as confirmative diagnostic method was valuable in 12(38.7%) of 31 patients who's etiology was identified. Of 53 patients, 22 persons (41.5%) showed no abnormal findings in marrow. CONCLUSION: Bone marrow study for FUO was very useful to diagnose hematologic diseases and miliary tuberculosis, but it was considered to be a less useful method for the initial diagnosis for the other diseases.