Annals of clinical biochemistry
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Ann. Clin. Biochem. · Nov 2016
Analytical performance specifications for changes in assay bias (Δbias) for data with logarithmic distributions as assessed by effects on reference change values.
Background The distributions of within-subject biological variation are usually described as coefficients of variation, as are analytical performance specifications for bias, imprecision and other characteristics. Estimation of specifications required for reference change values is traditionally done using relationship between the batch-related changes during routine performance, described as Δbias, and the coefficients of variation for analytical imprecision (CVA): the original theory is based on standard deviations or coefficients of variation calculated as if distributions were Gaussian. Methods The distribution of between-subject biological variation can generally be described as log-Gaussian. ⋯ The model was tested using plasma prolactin and glucose as examples. Results Analytical performance specifications for reference change value generated using the new model based on log-Gaussian distributions were practically identical with the traditional model based on Gaussian distributions. Conclusion The traditional and simple to apply model used to generate analytical performance specifications for reference change value, based on the use of coefficients of variation and assuming Gaussian distributions for both CVI and CVA, is generally useful.
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Ann. Clin. Biochem. · Mar 2016
Rapid and sensitive analysis of reduced and oxidized coenzyme Q10 in human plasma by ultra performance liquid chromatography-tandem mass spectrometry and application to studies in healthy human subjects.
Coenzyme Q10 is an endogenous antioxidant as well as a popular dietary supplement. In blood circulation, coenzyme Q10 exists predominantly as its reduced ubiquinol-10 form, which readily oxidizes to ubiquinone-10 ex vivo. Plasma concentrations of coenzyme Q10 reflect net overall metabolic demand, and the ratio of ubiquinol-10:ubiquinone-10 has been established as an important biomarker for oxidative stress. However, the lability of ubiquinol-10 makes accurate determination of both forms of coenzyme Q10 difficult. Ex vivo oxidation of ubiquinol-10 to ubiquinone-10 during sample collection, processing and analysis may obfuscate the in vivo ratio. ⋯ This method is suitable for clinical studies with coenzyme Q10 supplementation in various disease states where this lipid-antioxidant may be beneficial. We have applied this method to >300 plasma samples from coenzyme Q10 research studies in chronic haemodialysis patients and postsurgical patients.
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Ann. Clin. Biochem. · Jan 2016
Comparative StudyAnalysis of cerebrospinal fluid for xanthochromia versus modern computed tomography scanners in the diagnosis of subarachnoid haemorrhage: experience at a tertiary trauma referral centre.
Diagnosis of subarachnoid haemorrhage, a neurosurgical emergency in patients with headache remains a logistical challenge. The rationale of the traditional pathway of cerebrospinal fluid xanthochromia analysis following negative computed tomography head scans to exclude subarachnoid haemorrhage has been challenged by the increasing accuracy of modern computed tomography scanners. ⋯ Despite improved computed tomography scanning technology, cerebrospinal fluid xanthochromia interpretation aids in the definitive diagnosis of subarachnoid haemorrhage. When requested appropriately cerebrospinal fluid xanthochromia analysis remains a vital service as results impact on clinical decision making, especially when computed tomography scan results are equivocal and is also important in later presenting patients when computed tomography accuracy decreases.
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Ann. Clin. Biochem. · Jan 2016
Cystatin C- and creatinine-based equations in the assessment of renal function in HIV-positive patients prior to commencing Highly Active Antiretroviral Therapy.
We evaluated the accuracy and precision of creatinine- and cystatin C-based prediction equations for estimating glomerular filtration rate compared to measured glomerular filtration rate in an antiretroviral-naive human immunodeficiency virus population. ⋯ Sensitivity of creatinine-based equations for predicting glomerular filtration rate was poor in this group of patients. The CKD-EPIcombined equation performed better than creatinine-based equations.
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Ann. Clin. Biochem. · Jan 2016
Comparative StudyPneumatic tube transport of blood-stained cerebrospinal fluid specimens has no clinically relevant effect on rates of haemolysis compared to manual transport.
Pneumatic tube transport of pathology specimens from the emergency department to the laboratory for analysis is a widely used practice. When compared to manual specimen transport, it results in savings in both time and labour. Sampling of cerebrospinal fluid still forms part of the workup of patients with suspected subarachnoid haemorrhage. There are claims in the literature that transport of cerebrospinal fluid samples by pneumatic tube results in excess haemolysis, which interferes with cerebrospinal fluid analysis for the presence of bilirubin. The aim of our study was to ascertain whether pneumatic tube transport of blood-stained cerebrospinal fluid to the laboratory, results in clinically significantly higher levels of haemolysis compared with manual transport of the same specimens. ⋯ Pneumatic tube transport of cerebrospinal fluid to the laboratory is not associated with clinically significantly higher rates of haemolysis when compared to manual transport.