BACKGROUND: Simple manual method using a Nageotte hemocytometer counting residual leukocytes [White blood cells(WBC)] in blood components is subjective, labor-intensive, time consuming and variable within and between laboratories. The aim of this study was to evaluate usefulness for flow cytometric method to determinate very low numbers of leukocytes in leukocyte-free blood components. METHODS: Epics XL-MCL (Beckman Coulter Co.) was used for determination of fluorescence-labelled cells. The DNA in leukocytes was stained using propidium iodide (PI) and leukocytes were automatically analysed by flow cytometer. RESULTS: Linearity determined over a range of 0.5-50 WBC/muL was a value of r=0.994. The detection limit of this method was 4.4 WBC/muL and accuracy was 86.6% with linearity of r=0.991 over the 5-50 WBC/muL. Reproducibility was CV of 9.1% for 25.8 WBC/muL and 14.7% for 7.1 WBC/muL, respectively. CONCLUSION: Flow cytometric techniques provide a reproducible and objective tool for counting residual WBC in leukocyte free blood components compared with the Nageotte hemocytometer.
DNA ; Leukocytes* ; Limit of Detection ; Propidium

OBJECTIVES: Rapid increase in engineered nanoparticles (ENPs) in many goods has raised significant concern about their environmental safety. Proper methodologies are therefore needed to conduct toxicity and exposure assessment of nanoparticles in the environment. This study reviews several analytical techniques for nanoparticles and summarizes their principles, advantages and disadvantages, reviews the state of the art, and offers the perspectives of nanometrology in relation to ENP studies. METHODS: Nanometrology is divided into five techniques with regard to the instrumental principle: microscopy, light scattering, spectroscopy, separation, and single particle inductively coupled plasma-mass spectrometry. RESULTS: Each analytical method has its own drawbacks, such as detection limit, ability to quantify or qualify ENPs, and matrix effects. More than two different analytical methods should be used to better characterize ENPs. CONCLUSIONS: In characterizing ENPs, the researchers should understand the nanometrology and its demerits, as well as its merits, to properly interpret their experimental results. Challenges lie in the nanometrology and pretreatment of ENPs from various matrices; in the extraction without dissolution or aggregation, and concentration of ENPs to satisfy the instrumental detection limit.
Limit of Detection ; Microscopy ; Nanoparticles ; Spectrum Analysis

A method of detecting lead was developed using square wave anodic stripping voltammetry (SWASV) with DNA-carbon nanotube paste electrode (CNTPE). The results indicated a sensitive oxidation peak current of lead on the DNA-CNTPE. The curves were obtained within a concentration range of 50 ngL-1-20 mgL-1 with preconcentration time of 100, 200, and 400 sec at the concentration of mgL-1, microgL-1, and ngL-1, respectively. The observed relative standard deviation was 0.101% (n = 12) in the lead concentration of 30.0 microgL-1 under optimum conditions. The low detection limit (S/N) was pegged at 8 ngL-1 (2.6 x10-8 M). Results showed that the developed method can be used in real-time assay in vivo without requiring any pretreatment and pharmaceutical samples, and food samples, as well as other materials requiring water source contamination analyses.
Electrodes ; Limit of Detection ; Nanotubes ; Plants* ; Water

AIMTo establish a fluorospectrophotometric assay for the measurement of nitrite in blood.

METHODSInterference from hemoglobin and other blood ingredients was removed through sulfuric acid and phosphotungstic acid pretreatment. Fluorescence of 1-[H]-naphthotriazole from the reaction of 2,3-diaminonaphthalene with nitrite was determined with fluorospectrophotometry.

RESULTSThe following conditions were proper: Serum or plasma was treated with sulfuric acid and phosphotungstic acid pretreatment for two times, 2,3-diaminonaphthalene of 0.63 mmol x (L(-1)) was used, reaction solution pH and final pH were about 1.60 and 1.70 respectively, solution containing 2,3-diaminonaphthalene and supernatant after pretreatment was water-bathed at 20 degrees C for 15 minutes. The lower limit of detection was 24.27 nmol x L(-1). Nitrite determined in peripheral blood of healthy people was (10.91 +/- 2.38) micromol x L(-1), and its 95% distribution range was (6.24-15.57) micromol x L(-1).

CONCLUSIONIt's a relatively sensitive, specific, simple method. It's of some value to the study of nitric oxide.

BACKGROUND: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) are used increasingly for tacrolimus monitoring. However, there are still variability of results due to home-brew reagents, so which cannot be warrantable data. We evaluated the analytical performance and clinical usefulness of a newly introduced MassTrak LC/MS/MS Tacrolimus kit (Waters Corporation, USA). METHODS: The performance of LC-MS/MS for determination of tacrolimus concentration were analyzed using patient samples and MassTrak LC/MS/MS Tacrolimus kit including calibrators, quality controls, internal standard, column and neat solution with respect to linearity, precision, lower limit of detection, lower limit of quantitation, sample carryover and comparison according to CLSI guidelines. The LC-MS/MS using home-brew reagents were performed for comparison test. RESULTS: The LC-MS/MS using MassTrak LC/MS/MS Tacrolimus kit showed a good linearity (R2> or =0.997) and precision (CV< 8%). Assigned LLOD (0.4 ng/mL) and LLOQ (0.8 ng/mL) were validated and carryover was estimated 0.5%. The system correlated well with the LC-MS/MS using home-brew reagents (R> or =0.974). CONCLUSIONS: LC-MS/MS using MassTrak LC/MS/MS Tacrolimus kit for determination of tacrolimus concentration showed good performance for linearity, precision, LLOD, LLOQ, carryover and comparison. Introduction of MassTrak LC/MS/MS Tacrolimus kit could be warranted results by manufacturer and useful for management of quality control.
Humans ; Indicators and Reagents ; Limit of Detection ; Mass Spectrometry ; Quality Control ; Tacrolimus

One-step real-time reverse transcription-polymerase chain reaction (RT-PCR) assay using the MagNA Pure LC and LightCycler(TM) system was developed and validated for the detection and quantitation of hepatitis A virus (HAV) RNA. The assay was evaluated using in-house synthetic HAV RNA standard. The real-time RT-PCR assay could quantitate a dynamic range of HAV RNA standard between 10(2) and 10(8) copies per reaction. The regression coefficient of the standard curve was an 0.99. The detection limit of the assay was 31.3 RNA copies per reaction. The coefficient variations (CVs) of the assay in combination with automated RNA extraction were less than 1.91% in both intra- and inter-assay. The real-time RT-PCR assay for quantitative detection of HAV would serve a useful method for improving the safety of biological products.
Biological Products ; Hepatitis A virus* ; Hepatitis A* ; Hepatitis* ; Limit of Detection ; RNA*

Salmonella are causative agents of gastroenteritis and systemic disease in animals. The invA gene was selected as a target sequence of loop-mediated isothermal amplification (LAMP) assay for diagnosis of Salmonella infection. The detection limits for broth dilution, spiked feces and enrichment were 10(4), 10(5) and 10(2) CFUs/mL, respectively. The LAMP assay developed in the present study may be a reliable method for detection of Salmonella spp. in pig feces.
Animals ; Diagnosis ; Feces* ; Gastroenteritis ; Limit of Detection ; Salmonella Infections ; Salmonella*

BACKGROUND: Fecal occult blood tests (FOBT) have been recommended for gastro- intestinal bleeding and colon cancer screening. This study compared the effectiveness of two fecal blood screening kit, OC-Hemodia II and Ez step FOB for fecal occult blood. METHODS: The detection limit was evaluated by using OC-control and serially diluted samples. The comparison study between OC-hemodia II and Ez step FOB were evaluated in 143 cases. RESULTS: The concordance rate between OC-Hemodia II and Ez step FOB was 85.6% and 50% of non-concordance cases have history related to gatrointestinal bleeding. Ez step FOB was possible to detect 35 ng/mL in serially diluted OC-control. CONCLUSIONS: The result of Ez step FOB satisfactory to clinical application and showed good concordance rate compared to OC-Hemodia II.
Colonic Neoplasms ; Hemorrhage ; Limit of Detection ; Mass Screening ; Occult Blood*

OBJECTIVES: This study was conducted to validate a simple, rapid and sensitive reverse-phase high-performance liquid chromatographic method with UV detector (HPLC-UV) and present the plasma level of di(2-ethylhexyl)phthalate (DEHP) in some Korean male workers. METHODS: HPLC-UV for quantification of plasma DEHP was validated by the following guideline from the Center for Drug Evaluation and Research (CDER)-calibration/standard curve, precision, accuracy and recovery. Plasma DEHP from 255 healthy Korean male workers aged from 30 to 60 years was analyzed by validated HPLC-UV method. RESULTS: The calibration curve over the range 0~150 microgram/liter for the plasma DEHP standard solution showed linearity(r2=0.999). The limit of detection (LOD) and limit of quantification (LOQ) of plasma DEHP were 5.22 microgram/liter and 15.81 microgram/liter, respectively. The accuracy and precision for 2.5 microgram/liter of DEHP were acceptable in CDER guideline on the second and third day but not first day, and those for 50 microgram/liter and 150 microgram/liter of DEHP were acceptable on all three days(Ed-confirm this addition). The distribution of plasma DEHP level was skewed to the left and ranged from 0 to 18.9 microgram/liter. The plasma DEHP level was lower than 10 microgram/liter for 98 % of subjects and lower than 5 microgram/liter for 85 %. The geometric mean and standard deviation of plasma DEHP were 0.4 +/- 1.5 microgram/liter. CONCLUSIONS: The HPLC-UV method for quantification of plasma DEHP was acceptable by CDER guideline. The plasma DEHP of 255 Korean male workers ranged from 0 to 18.9 microgram/liter and the distribution was skewed to the left.
Calibration ; Diethylhexyl Phthalate ; Drug Evaluation ; Humans ; Limit of Detection ; Male* ; Plasma*

BACKGROUND: C-reactive protein (CRP) concentrations are measured by two different assays depending on the clinical concern: the conventional CRP assay for estimating the extent of inflammation and the high sensitivity-CRP (hs-CRP) assay for assessing the risk of cardiovascular diseases. To integrate the conventional CRP test detecting acute phase response and the hs-CRP assay with a lower detection limit, we evaluated the performance characteristics of hs-CRP assay methods with a wide range of concentrations. METHODS: Immunonephelometric assay (BNII) and two turbidoimmunometric assays (TIA), the Hitachi 7600 with Daiichi reagent (Daiichi-Hitachi) and the Roche Cobas Integra 700 (Integra), were evaluated for the precision with 8 levels of pooled sera ranging from 0.3 to 120 mg/L and the agreement of TIA with the BNII assay using regression analysis and Bland-Altman analysis with 89 patient samples. RESULTS: The within-day coefficients of variation (CVs) of BNII were less than 10% in all levels of pooled sera. The CVs of Daiichi-Hitachi and Integra exceeded 10% in pooled sera below 1.0 mg/L and 0.5 mg/L, respectively. Both Daiichi-Hitachi and Integra appeared to be linear over the entire range of CRP concentrations used and were comparable with the results of BNII (Daiichi-Hitachi: y=0.98x+0.13, r=0.97, Integra; y=1.02x+0.22, r=0.99). However, at the concentrations over 100 mg/L TIA and BNII showed discrepant results. CONCLUSIONS: Both Daiichi-Hitachi and Integra showed a good precision over a wide range of CRP. However, the discrepant results found at very high concentrations require standardization among different assay methods or instruments.
C-Reactive Protein* ; Cardiovascular Diseases ; Humans ; Inflammation ; Limit of Detection