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- Bjerner, Johan, et al.
(författare)
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Non-parametric estimation of reference intervals in small non-Gaussian sample sets
- 2009
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Ingår i: ACCREDITATION AND QUALITY ASSURANCE. - : Springer Science and Business Media LLC. - 0949-1775 .- 1432-0517. ; 14:4, s. 185-192
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed at validating common bootstrap algorithms for reference interval calculation.We simulated 1500 random sets of 50-120 results originating from eight different statistical distributions. In total, 97.5 percentile reference limits were estimated from bootstrapping 5000 replicates, with confidence limits obtained by: (a) normal, (b) from standard error, (c) bootstrap percentile (as in RefVal) (d) BCa, (e) basic, or (f) student methods. Reference interval estimates obtained with ordinary bootstrapping and confidence intervals by percentile method were accurate for distributions close to normality and devoid of outliers, but not for log-normal distributions with outliers. Outlier removal and transformation to normality improved reference interval estimation, and the basic method was superior in such cases. In conclusions, if the neighborhood of the relevant percentile contains non-normally distributed results, bootstrapping fails. The distribution of bootstrap estimates should be plotted, and a non-normal distribution should warrant transformation or outlier removal.
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| 2. |
- Fischer, C.P, et al.
(författare)
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Vitamin E isoform-specific inhibition of the exercise-induced heat shock protein 72 expression in humans
- 2006
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 100:5, s. 1679-1687
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Tidskriftsartikel (refereegranskat)abstract
- Increased levels of reactive oxygen and nitrogen species, as seen in response to exercise, challenge the cellular integrity. Important protective adaptive changes include induction of heat shock proteins (HSPs). We hypothesized that supplementation with antioxidant vitamins C (ascorbic acid) and E (tocopherol) would attenuate the exercise-induced increase of HSP72 in the skeletal muscle and in the circulation. Using randomization, we allocated 21 young men into three groups receiving one of the following oral supplementations: RRR-α-tocopherol 400 IU/ day + ascorbic acid (AA) 500 mg/day (CEα), RRR-α-tocopherol 290 IU/day + RRR-γ-tocopherol 130 IU/day + AA 500 mg/day (CEαγ), or placebo (Control). After 28 days of supplementation, the subjects performed 3 h of knee extensor exercise at 50% of the maximal power output. HSP72 mRNA and protein content was determined in muscle biopsies obtained from vastus lateralis at rest (0 h), postexercise (3 h), and after a 3-h recovery (6 h). In addition, blood was sampled for measurements of HSP72, α-tocopherol, γ-tocopherol, AA, and 8-isoprostaglandin-F2α (8-PGF2α). Postsupplementation, the groups differed with respect to plasma vitamin levels. The marker of lipid peroxidation, 8-iso-PGF2α, increased from 0 h to 3 h in all groups, however, markedly less (P < 0.05) in CEα. In Control, skeletal muscle HSP72 mRNA content increased 2.5-fold (P < 0.05) and serum HSP72 protein increased 4-fold (P < 0.05) in response to exercise, whereas a significant increase of skeletal muscle HSP72 protein content was not observed (P = 0.07). In CEα, skeletal muscle HSP72 mRNA, HSP72 protein, and serum HSP72 were not different from Control in response to exercise. In contrast, the effect of exercise on skeletal muscle HSP72 mRNA and protein, as well as circulating HSP72, was completely blunted in CEαγ. The results indicate that γ-tocopherol comprises a potent inhibitor of the exercise-induced increase of HSP72 in skeletal muscle as well as in the circulation.
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| 3. |
- Forsum, Urban, 1946-, et al.
(författare)
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The impact of qualitative analysis in laboratory medicine
- 2005
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Ingår i: TrAC. Trends in analytical chemistry. - : Elsevier BV. - 0165-9936 .- 1879-3142. ; 24:6, s. 546-555
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory medicine is a challenge for the metrologically and terminologically inclined scientist. One main reason is the need for a sound theory that can be applied in a systematic way to cover all aspects of examinations, i.e., those procedures whose results are reported on an ordinal scale and those reported on more primitive scales (e.g., classifications and narratives). Validation of procedures for examinations involving properties on a nominal scale is especially difficult to achieve because it is hard to find gold standards, in the conventional sense, against which to validate and which combine performance characteristics and clinically relevant specificity and sensitivity. We present a systematic, unambiguously defined terminology (the C-NPU coding scheme) for metrologically derived terms for expressing properties, and present some examples of how to attain diagnostic goals. If the analytic process in the laboratory can be subsumed into medical contexts in a systematic way, many pitfalls in reporting results can be avoided. © 2005 Elsevier Ltd. All rights reserved.
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| 4. |
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| 5. |
- Törner, Anna, et al.
(författare)
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Renal function in community-dwelling frail elderly : comparison between measured and predicted glomerular filtration rate in the elderly and proposal for a new cystatin C-based prediction equation
- 2008
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Ingår i: Aging Clinical and Experimental Research. - Milano : Editrice Kurtis. - 1594-0667 .- 1720-8319. ; 20:3, s. 216-225
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND AIMS: There is a great need to evaluate renal function regularly in elderly people. This study aimed at analyzing renal function in stable, community-dwelling elderly people of 75 years and over, to compare measured and predicted glomerular filtration rates (GFR) and to develop an accurate prediction equation for this age group. METHODS: Forty-five ambulatory elderly people in stable health in ordinary living were randomly selected into four age-classes, aged 75-95. Demographic data, personal activities of daily living, continuous drug prescriptions, body composition, blood pressure and blood chemistry were analysed. GFR was measured as Iohexol clearance based on three time-points 3, 4 and 7 hours after Iohexol injection. RESULTS: Mean GFR was well preserved in all four age-classes. The GFR range was 18-83 mL/min and declined with age. The Cockcroft-Gault prediction equation systematically underestimated measured GFR. A new 'GFRA' prediction equation is presented, based on the inverse of serum cystatin C and independent of gender, body surface area, body weight, lean body mass or serum creatinine. The proposed equation underestimated measured GFR with a mean of only 0.1 mL/min, had better precision compared with the Cockcroft-Gault equation, and was evaluated by the method of cross-validation. CONCLUSIONS: GFR exhibits extensive heterogeneity in frail, community-dwelling elderly people. The proposed GFRA was clearly more precise than the Cockcroft-Gault prediction equation in the study group. However, it needs to be validated in a larger population of elderly subjects, including more individuals in stable health with substantially reduced renal function in whom GFR is measured by a reference method with adequate sampling time.
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