| 1. |
|
|
| 2. |
- Baxter, Douglas, et al.
(author)
-
Methylmercury measurement in whole blood by isotope-dilution GC-ICPMS with 2 sample preparation methods
- 2007
-
In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:1, s. 111-116
-
Journal article (peer-reviewed)abstract
- Background: Despite its known toxicity, methylmercury is rarely measured directly in clinical studies; instead, conclusions are based on total mercury measurements. We have developed isotope-dilution-based methods for methylmercury-specific analysis of whole blood by coupled gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS). Methods: We analyzed animal and human blood samples after alkaline digestion or extraction of methylmercury into dichloromethane and back extraction into water. Methylmercury was converted to the volatile ethyl derivative, purged, and trapped on a solid-phase collection medium, and then introduced into the GC-ICPMS system. Results: Limits of quantification were 0.4 and 0.03 mu g/L at a signal-to-noise ratio of 10 with the alkaline digestion and extraction methods, respectively. Extraction met our selected acceptable total error criterion, with an SD of 0.58 mu g/L at the critical maternal blood concentration of 5.8 mu g/L.Results obtained with alkaline digestion indicated the need for improved random analytical uncertainty, which was achieved by increasing the enrichment of the isotope dilution. For 37 blood samples, the mean (SD) proportion of total mercury present as methylmercury was 60 (27)%, range 6%-100%.Conclusions: The combination of extraction and isotope-dilution GC-ICPMS meets the requirements for use as a reference method for measuring methylmercury in whole blood.
|
|
| 3. |
|
|
| 4. |
- Clarke, Robert, et al.
(author)
-
Detection of vitamin B12 deficiency in older people by measuring vitamin B12 or the active fraction of vitamin B12, holotranscobalamin.
- 2007
-
In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:5, s. 963-970
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Impaired vitamin B(12) function and decreased vitamin B(12) status have been associated with neurological and cognitive impairment. Current assays analyze total vitamin B(12) concentration, only a small percentage of which is metabolically active. Concentrations of this active component, carried on holotranscobalamin (holoTC), may be of greater relevance than total vitamin B(12). METHODS: We compared the utility of serum holoTC with conventional vitamin B(12) for detection of vitamin B(12) deficiency in a population-based study of older people, using increased methylmalonic acid (MMA) concentrations as a marker of metabolic vitamin B(12) deficiency in the overall population (n = 2403) and in subsets with normal (n = 1651) and abnormal (n = 752) renal function. RESULTS: Among all participants, 6% had definite (MMA >0.75 micromol/L) and 16% had probable (MMA >0.45 micromol/L) metabolic vitamin B(12) deficiency. In receiver operating characteristic curves for detection of definite vitamin B(12) deficiency, holoTC had a greater area under the curve (AUC) compared with vitamin B(12) in all participants (0.85 vs 0.76; P <0.001) and in subsets with normal (AUC: 0.87 vs 0.79; P <0.001) and abnormal (AUC: 0.85 vs 0.74; P = 0.002) renal function. Similar findings were observed for detection of moderate vitamin B(12) deficiency. Whereas the positive predictive value for both holoTC and vitamin B(12) was greater for detection of probable than definite vitamin B(12) deficiency, both tests were associated with more false-positive than true-positive test results. CONCLUSIONS: HoloTC has a modestly superior diagnostic accuracy compared with conventional vitamin B(12) for the detection of vitamin B(12) deficiency, but neither test can be recommended to screen asymptomatic populations.
|
|
| 5. |
- Kempf, Tibor, et al.
(author)
-
Circulating concentrations of growth-differentiation factor 15 in apparently healthy elderly individuals and patients with chronic heart failure as assessed by a new immunoradiometric sandwich assay
- 2007
-
In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:2, s. 284-291
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Growth-differentiation factor 15 (GDF15) is a member of the transforming growth factor beta (TGF-beta) cytokine superfamily. There has been increasing interest in using circulating GDF15 as a biomarker in patients, for example those with cardiovascular disease. METHODS: We developed an IRMA that uses a polyclonal, affinity chromatography-purified goat antihuman GDF15 IgG antibody, assessed the preanalytic characteristics of GDF15, and determined circulating GDF15 concentrations in 429 apparently healthy elderly individuals and 153 patients with chronic heart failure (CHF). RESULTS: The assay had a detection limit of 20 ng/L, an intraassay imprecision of < or =10.6%, and an interassay imprecision of < or =12.2%. Specificity was demonstrated with size-exclusion chromatography, parallel measurements with polyclonal and monoclonal anti-GDF15 antibody, and lack of cross-reactivity with TGF-beta. The assay was not appreciably influenced by the anticoagulant matrix or unrelated biological substances. GDF15 was stable at room temperature for 48 h and resistant to 4 freeze-thaw cycles. Apparently healthy, elderly individuals presented with a median GDF15 concentration of 762 ng/L (25th-75th percentiles, 600-959 ng/L). GDF15 concentrations were associated with age and with cystatin C and C-reactive protein concentrations. CHF patients had increased GDF15 concentrations that were closely related to disease severity. CONCLUSION: The IRMA can detect GDF15 in human serum and plasma with excellent sensitivity and specificity. The reference limits and confounding variables defined for apparently healthy elderly individuals and the favorable preanalytic characteristics of GDF15 are expected to facilitate future studies of GDF15 as a biomarker in various disease settings, including CHF.
|
|
| 6. |
|
|
| 7. |
- Plymoth, Amelie, et al.
(author)
-
Protein expression patterns associated with progression of chronic obstructive pulmonary disease in bronchoalveolar lavage of smokers
- 2007
-
In: Clin Chem. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:4, s. 636-44
-
Journal article (peer-reviewed)abstract
- BACKGROUND: We modeled the expression of proteins in baseline bronchoalveolar lavage (BAL) samples from asymptomatic 60-year-old lifelong current smokers or healthy never-smokers, who were reevaluated after 6 to 7 years to record clinical outcome. METHODS: Applying a technology toolbox consisting of replicate 2-dimensional gel separations, image annotation, and mass spectrometry identification, we catalogued a global set of proteins that were differentially expressed in individuals by presence, absence, and intensity scores. RESULTS: By use of multivariate analysis, we selected a subset of proteins that accurately separated smokers from never-smokers based on composite scoring. Follow-up after 6 to 7 years identified a group of individuals who had progressed to chronic obstructive pulmonary disease (COPD), Global Initiative for Chronic Obstructive Lung Disease stage 2. The baseline BAL samples of these eventual COPD patients shared a distinct protein expression profile that could be identified using partial least-squares discriminant analysis. This pattern was not observed in BAL samples of asymptomatic smokers free of COPD at 6- to 7-year follow-up. CONCLUSIONS: Our model suggests that certain patterns of protein expression occurring in the airways of long-term smokers may be detected in smokers susceptible to a progression of COPD disease, before disease is clinically evident.
|
|
| 8. |
- Rundström, Gerd, et al.
(author)
-
Lateral Flow Immunoassay Using Europium (III) Chelate Microparticles and Time-Resolved Fluorescence for Eosinophils and Neutrophils in Whole Blood
- 2007
-
In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:2, s. 342-348
-
Journal article (peer-reviewed)abstract
- Background: A simple point-of-care method for measuring leukocyte counts in a doctor’s office or emergency room could be of great importance. We developed a protocol for measuring cell count by disrupting the cell membrane and analyzing specific proteins within the cells and used it to analyze proteins from eosinophils and neutrophils. Methods: Lateral immunochromatographic (ICR) assays have been developed for eosinophil protein X (EPX) and human neutrophil lipocalin (HNL) as measures of the concentration of eosinophils and neutrophils. The correlation between the lateral ICR assays and cell counting of eosinophils and neutrophils was performed manually and with an automated cell counter. RIA assays measuring the same analytes were also compared with the results from cell counting and lateral ICR assays. Results: The optimized assays showed analytical detection limits below the clinical ranges of 3.36 µg/L and 2.05 µg/L for EPX and HNL, respectively. The recovery was 114.8%–122.8% for EPX and 94.5%–96.9% for HNL. The imprecision was 3%–17% CV for EPX over the whole range and 5%–16% CV for HNL. The correlation coefficients between manually counted cells and lateral ICR assays were 0.9 and 0.83 for EPX and HNL, respectively. Conclusion: The numbers of eosinophils and neutrophils in small amounts of blood can be estimated in the point-of-care setting by means of fast lateral ICR assays of EPX and HNL.
|
|
| 9. |
- Sjöholm, Malin, et al.
(author)
-
Assessing Quality and Functionality of DNA from Fresh and Archival Dried Blood Spots and Recommendations for Quality Control Guidelines.
- 2007
-
In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53, s. 1401-1407
-
Journal article (peer-reviewed)abstract
- Background: Dried blood spots (DBS) are a convenient and inexpensive method for biobanking. Although many countries have established population-based DBS biobanks from neonatal screening programs, the quality and usefulness of DNA from DBS have not been extensively assessed. Methods: We compared 4 common DNA extraction methods (Qiagen, EZNA, Chelex 100, and alkaline lysis) in a pilot study using fresh DBS with known lymphocyte count. We assessed suitability for multiple displacement amplification (MDA) and subsequent single-nucleotide polymorphism (SNP) analyses. We selected the EZNA method for DNA extraction from archival samples up to 27 years old, stored at room temperature or –20 °C, and SNP analyses were performed after MDA. Results: Extraction using alkaline lysis failed in most tests, and Chelex 100 was unsuccessful in real-time PCR, whereas the EZNA and Qiagen methods were successful by all evaluated quality indices. DNA extraction by EZNA, MDA, and SNP analyses were successful for the archival samples stored at –20 °C. Conclusion: Routine protocols for evaluation of the quality and functional integrity of DNA based on DNA yield, DNA size, and quantification of amplifiable DNA allow use of sufficient template for MDA and successful SNP analyses from both primary DBS extract and MDA product. A single 3-mm disc can yield sufficient DNA for several thousand SNP analyses. DNA from DBS is thus suitable for genetic epidemiology studies.
|
|
| 10. |
- Steuber, Thomas, et al.
(author)
-
Comparison of free and total forms of serum human kallikrein 2 and prostate-specific antigen for prediction of locally advanced and recurrent prostate cancer
- 2007
-
In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:2, s. 233-240
-
Journal article (peer-reviewed)abstract
- Background: We evaluated the association of total and free forms of serum human kallikrein 2 (hK2) and prostate-specific antigen (PSA) with prostate cancers of unfavorable prognosis. Methods: We retrospectively measured total PSA (tPSA), free PSA (fPSA), and total hK2 (thK2) in preoperative serum samples from 867 men [and assessed free hK2 (fhK2) measured in 577 of these men] treated with radical prostatectomy for clinically localized prostate cancer. Associations between biomarker concentrations and extracapsular extension, seminal vesicle invasion, and biochemical recurrence (BCR) were evaluated. A subset of patients with PSA <= 10 mu g/L, the group most commonly seen in clinical practice in the US, was analyzed. Results: thK2 was the strongest predictor of extracapsular extension and seminal vesicle invasion (areas under the ROC curve [AUC], 0.662 and 0.719, respectively), followed by tPSA (AUC, 0.654 and 0.663). All biomarkers were significant predictors of BCR. hK2 forms, but not PSA forms, remained highly significant for predicting BCR in the low-PSA group. Combining tPSA, fPSA, and thK2 in a multivariable model improved prediction compared with any biomarker used individually (AUC, 0.711, 0.755, and 0.752 for this combination predicting extracapsular extension, seminal vesicle invasion, and BCR, respectively; P < 0.001 for all). Conclusions: Increased concentrations of hK2 in the blood are significantly associated with unfavorable features of prostate cancer, and thK2 is predictive of locally advanced and recurrent cancer in patients with PSA <= <= 10 mu g/L. Independent of tPSA and fPSA, hK2 predicts unfavorable prognosis. (c) 2007 American Association for Clinical Chemistry
|
|
