Testosterone Measured with an Automatic Immunoassay Compares Reasonably Well to Results Obtained by LC-MS/MS.

BACKGROUND: Previous studies have reported problems measuring testosterone with immunological assays. Here we explore an automatic second generation immunoassay compared to a LC-MS/MS method. METHODS: We collected blood samples from 76 women and measured testosterone, progesterone, gender hormonebinding globulin (SHBG), and albumin employing Cobas e601/c501. Testosterone, androstenedione (andro), dehydroepiandrosterone sulphate (DHEAS), and 17-hydroxyprogesterone (17-OHP) concentrations were measured employing LC-MS/MS. We evaluated the difference between testosterone measured by the two methods and examined the potential interference from the selected steroids and bindings proteins. RESULTS: Testosterone concentrations measured by the two methods yielded: Cobas e601 = 1.240 x (LC-MS/MS) - 0.197, r = 0.84, for testosterone concentrations between 0.22 - 4.9 nmol/L. A positive correlation was observed for the difference between results obtained by the two methods and the sample concentration of DHEAS and andro: Diff (Cobas e601 - LC-MS/MS) = 0.116 x DHEAS - 0.396, r = 0.84 and Diff (Cobas e601 - LC-MS/MS) = 0.08 andro - 0.380, r = 0.58. No statistically significant interference was observed for progesterone, 17-OHP, SHBG, and albumin. CONCLUSIONS: We report significant differences between testosterone measurements employing an automatic second generation immunoassay and LC-MS/MS. The difference can be correlated with the measured concentrations of DHEAS and andro, and its magnitude is judged to be of limited clinical relevance. Thus we judge that the automatic second generation immunoassay can be used for routine measurement of testosterone.

Reference intervals and stability of haptocorrin and holotranscobalamin in Danish children and elderly.

BACKGROUND: Haptocorrin (HC) and holotranscobalamin (holoTC) carry vitamin B12 (B12) in the circulation and can be useful biomarkers for evaluating B12 status. The concentration of both proteins depends on age, but data on reference intervals for children and the elderly are sparse. Similarly, not much is known about the effect of preanalytical factors. METHODS: HC plasma samples from healthy elderly > 65 years (n = 124) were analysed, and both HC and holoTC were analysed in paediatric serum samples ≤ 18 years (n = 400). Furthermore, we investigated assay precision and stability. RESULTS: HC and holoTC were effected by age. We established reference intervals for HC: 2-10 years, 369-1237 pmol/L; 11-18 years, 314-1128 pmol/L; 65-82 years, 242-680 pmol/L and for holoTC: 2-10 years, 46-206 pmol/L; 11-18 years, 30-178 pmol/L. Analytical coefficients of variations of 6.0-6.8% and 7.9-15.7% were found for HC and holoTC, respectively. HC were affected when stored at room temperature and by freeze/thaw. HoloTC was stable at room temperature and after delayed centrifugation. CONCLUSION: We present novel 95% age-related reference limits for HC and HoloTC in children, and for HC both in children and elderly. Moreover, we found HoloTC to be fairly stable when stored, whereas HC was more vulnerable to preanalytical factors.

Combining aryltriazenes and electrogenerated acids to create well-defined aryl-tethered films and patterns on surfaces.

Immobilization of submonolayers to 4-5 multilayers of organic molecules on carbon surfaces can be performed by in situ generation of aryl radicals from aryltriazenes. The central idea consists of oxidatively forming an electrogenerated acid of N,N'-diphenylhydrazine to convert the aryltriazene to the corresponding diazonium salt in the diffusion layer of the electrode. In a second step, the diazonium salt is reduced at the same electrode to give a surface of covalently attached aryl groups. In this manner, various moieties tethered to the aryl groups can be immobilized on the surface. Here a ferrocenyl group was introduced as redox marker, the electrochemical signal of which is extraordinarily well-defined. This behavior is independent of film thickness, the latter being easily controlled by the number of repetitive cycles performed. It is also demonstrated that the new approach is suitable for patterning of surfaces using scanning electrochemical microscopy.

The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers.

BACKGROUND: The cerebrospinal fluid (CSF) biomarkers amyloid ß (Aß)-42, total-tau (T-tau), and phosphorylated-tau (P-tau) demonstrate good diagnostic accuracy for Alzheimer's disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimer's Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch-to-batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program. METHODS: The program is open for laboratories using commercially available kits for Aß, T-tau, or P-tau. CSF samples (aliquots of pooled CSF) are sent for analysis several times a year from the Clinical Neurochemistry Laboratory at the Mölndal campus of the University of Gothenburg, Sweden. Each round consists of three quality control samples. RESULTS: Forty laboratories participated. Twenty-six used INNOTEST enzyme-linked immunosorbent assay kits, 14 used Luminex xMAP with the INNO-BIA AlzBio3 kit (both measure Aß-(1-42), P-tau(181P), and T-tau), and 5 used Meso Scale Discovery with the Aß triplex (AßN-42, AßN-40, and AßN-38) or T-tau kits. The total coefficients of variation between the laboratories were 13% to 36%. Five laboratories analyzed the samples six times on different occasions. Within-laboratory precisions differed considerably between biomarkers within individual laboratories. CONCLUSIONS: Measurements of CSF AD biomarkers show large between-laboratory variability, likely caused by factors related to analytical procedures and the analytical kits. Standardization of laboratory procedures and efforts by kit vendors to increase kit performance might lower variability, and will likely increase the usefulness of CSF AD biomarkers.

Reproductive death of cancer cells induced by femtosecond laser pulses.

PURPOSE: High intensity femtosecond (1 fs = 10(-15) s) laser pulses may, via multi-photon processes, cause reproductive cell death at wavelengths that otherwise are harmless. We study the efficacy of inducing reproductive death of cancer cells by ultraviolet (UV), visible (VIS) and near infrared (IR) femtosecond laser pulses. MATERIALS AND METHODS: Human squamous carcinoma cervical cancer cells are irradiated by femtosecond laser pulses at 800 nanometers (nm), 400 nm, 266 nm and 200 nm. The reproductive death is assessed by colony forming assay. The contribution from multi-photon processes is evaluated by comparing the cell reproduction subsequent to irradiation by collimated (low intensity) and focused (high intensity), pulsed laser beams with identical fluences. RESULTS: Suitable femtosecond pulses are capable of arresting cell reproduction at all the tested wavelengths. Irradiation at 266 nm is far more efficient than the other wavelengths, both in terms of the fluence and the absorbed dose needed to induce reproductive cell death. The collimated 800 nm beam is unable to induce reproductive cell death even at a fluence of 230 Joule/square centimeters (J/cm2). However, focused 800 nm pulses with much higher intensities, but lower fluences efficiently arrest cell reproduction, thus highlighting the dramatic effect of multi-photon processes. At the intensities used in the present work focusing the 400 nm beam improves its efficacy by an order of magnitude, whereas focusing the 266 nm beam does not improve its efficacy. CONCLUSION: Femtosecond pulses at 200, 266, 400 and 800 nm induce reproductive cell death if the intensity is sufficiently high. Multi-photon processes can improve the efficacy substantially and even result in reproductive cell death at wavelengths, where single-photon processes are harmless.