Inhibition of Piezo1 attenuates demyelination in the central nervous system.

Piezo1 is a mechanosensitive ion channel that facilitates the translation of extracellular mechanical cues to intracellular molecular signaling cascades through a process termed, mechanotransduction. In the central nervous system (CNS), mechanically gated ion channels are important regulators of neurodevelopmental processes such as axon guidance, neural stem cell differentiation, and myelination of axons by oligodendrocytes. Here, we present evidence that pharmacologically mediated overactivation of Piezo1 channels negatively regulates CNS myelination. Moreover, we found that the peptide GsMTx4, an antagonist of mechanosensitive cation channels such as Piezo1, is neuroprotective and prevents chemically induced demyelination. In contrast, the positive modulator of Piezo1 channel opening, Yoda-1, induces demyelination and neuronal damage. Using an ex vivo murine-derived organotypic cerebellar slice culture model, we demonstrate that GsMTx4 attenuates demyelination induced by the cytotoxic lipid, psychosine. Importantly, we confirmed the potential therapeutic effects of GsMTx4 peptide in vivo by co-administering it with lysophosphatidylcholine (LPC), via stereotactic injection, into the cerebral cortex of adult mice. GsMTx4 prevented both demyelination and neuronal damage usually caused by the intracortical injection of LPC in vivo; a well-characterized model of focal demyelination. GsMTx4 also attenuated both LPC-induced astrocyte toxicity and microglial reactivity within the lesion core. Overall, our data suggest that pharmacological activation of Piezo1 channels induces demyelination and that inhibition of mechanosensitive channels, using GsMTx4, may alleviate the secondary progressive neurodegeneration often present in the latter stages of demyelinating diseases.

Laboratory sample stability. Is it possible to define a consensus stability function? An example of five blood magnitudes.

BACKGROUND: The stability limit of an analyte in a biological sample can be defined as the time required until a measured property acquires a bias higher than a defined specification. Many studies assessing stability and presenting recommendations of stability limits are available, but differences among them are frequent. The aim of this study was to classify and to grade a set of bibliographic studies on the stability of five common blood measurands and subsequently generate a consensus stability function. METHODS: First, a bibliographic search was made for stability studies for five analytes in blood: alanine aminotransferase (ALT), glucose, phosphorus, potassium and prostate specific antigen (PSA). The quality of every study was evaluated using an in-house grading tool. Second, the different conditions of stability were uniformly defined and the percent deviation (PD%) over time for each analyte and condition were scattered while unifying studies with similar conditions. RESULTS: From the 37 articles considered as valid, up to 130 experiments were evaluated and 629 PD% data were included (106 for ALT, 180 for glucose, 113 for phosphorus, 145 for potassium and 85 for PSA). Consensus stability equations were established for glucose, potassium, phosphorus and PSA, but not for ALT. CONCLUSIONS: Time is the main variable affecting stability in medical laboratory samples. Bibliographic studies differ in recommedations of stability limits mainly because of different specifications for maximum allowable error. Definition of a consensus stability function in specific conditions can help laboratories define stability limits using their own quality specifications.

Spanish Preanalytical Quality Monitoring Program (SEQC), an overview of 12 years' experience.

BACKGROUND: Preanalytical variables, such as sample collection, handling and transport, may affect patient results. Preanalytical phase quality monitoring should be established in order to minimize laboratory errors and improve patient safety. METHODS: A retrospective study (2001-2013) of the results obtained through the Spanish Society of Clinical Biochemistry and Molecular Pathology (SEQC) External quality assessment (preanalytical phase) was performed to summarize data regarding the main factors affecting preanalytical phase quality. Our aim was to compare data from 2006 to 2013 with a previously published manuscript assessing the 2001-2005 period. RESULTS: A significant decrease in rejection rates was observed both for blood and urine samples. For serum samples, the most frequent rejection causes in the first period were non-received samples (37.5%), hemolysis (29.3%) and clotted samples (14.4%). Conversely, in the second period, hemolysis was the main rejection cause (36.2%), followed by non-received samples (34.5%) and clotted samples (11.1%). For urine samples, the main rejection cause overall was a non-received sample (up to 86.1% of cases in the second period, and 81.6% in the first). For blood samples with anticoagulant, the number of rejections also decreased. While plasma-citrate-ESR still showed the highest percentages of rejections (0.980% vs. 1.473%, p<0.001), the lowest corresponded to whole-blood EDTA (0.296% vs. 0.381%, p<0.001). CONCLUSIONS: For the majority of sample types, a decrease in preanalytical errors was confirmed. Improvements in organization, implementation of standardized procedures in the preanalytical phase, and participation in a Spanish external quality assessment scheme may have notably contributed to error reduction in this phase.

On the improvement of blood sample collection at clinical laboratories.

BACKGROUND: Blood samples are usually collected daily from different collection points, such hospitals and health centers, and transported to a core laboratory for testing. This paper presents a project to improve the collection routes of two of the largest clinical laboratories in Spain. These routes must be designed in a cost-efficient manner while satisfying two important constraints: (i) two-hour time windows between collection and delivery, and (ii) vehicle capacity. METHODS: A heuristic method based on a genetic algorithm has been designed to solve the problem of blood sample collection. The user enters the following information for each collection point: postal address, average collecting time, and average demand (in thermal containers). After implementing the algorithm using C programming, this is run and, in few seconds, it obtains optimal (or near-optimal) collection routes that specify the collection sequence for each vehicle. Different scenarios using various types of vehicles have been considered. Unless new collection points are added or problem parameters are changed substantially, routes need to be designed only once. RESULTS: The two laboratories in this study previously planned routes manually for 43 and 74 collection points, respectively. These routes were covered by an external carrier company. With the implementation of this algorithm, the number of routes could be reduced from ten to seven in one laboratory and from twelve to nine in the other, which represents significant annual savings in transportation costs. CONCLUSIONS: The algorithm presented can be easily implemented in other laboratories that face this type of problem, and it is particularly interesting and useful as the number of collection points increases. The method designs blood collection routes with reduced costs that meet the time and capacity constraints of the problem.

Current status of verification practices in clinical biochemistry in Spain.

BACKGROUND: Verification uses logical algorithms to detect potential errors before laboratory results are released to the clinician. Even though verification is one of the main processes in all laboratories, there is a lack of standardization mainly in the algorithms used and the criteria and verification limits applied. A survey in clinical laboratories in Spain was conducted in order to assess the verification process, particularly the use of autoverification. METHODS: Questionnaires were sent to the laboratories involved in the External Quality Assurance Program organized by the Spanish Society of Clinical Biochemistry and Molecular Pathology. Seven common biochemical parameters were included (glucose, cholesterol, triglycerides, creatinine, potassium, calcium, and alanine aminotransferase). RESULTS: Completed questionnaires were received from 85 laboratories. Nearly all the laboratories reported using the following seven verification criteria: internal quality control, instrument warnings, sample deterioration, reference limits, clinical data, concordance between parameters, and verification of results. The use of all verification criteria varied according to the type of verification (automatic, technical, or medical). Verification limits for these parameters are similar to biological reference ranges. Delta Check was used in 24% of laboratories. Most laboratories (64%) reported using autoverification systems. Autoverification use was related to laboratory size, ownership, and type of laboratory information system, but amount of use (percentage of test autoverified) was not related to laboratory size. CONCLUSIONS: A total of 36% of Spanish laboratories do not use autoverification, despite the general implementation of laboratory information systems, most of them, with autoverification ability. Criteria and rules for seven routine biochemical tests were obtained.

The search for a new marker of renal function in older patients with chronic kidney disease stages 3-4: usefulness of cystatin C-based equations.

BACKGROUND/AIM: Cystatin C (Cys C) is an endogenous marker of glomerular filtration rate (GFR) unaffected by body composition. The aim of the present study was to assess the utility of Cys C-based GFR prediction equations (Hoek, Larsson and Stevens) and creatinine (modification of diet in renal disease-isotope dilution mass spectrometry--MDRD-IDMS, and Cockcroft-Gault--CG) compared with 51Cr-EDTA. METHODS: This study was carried out in 40 Caucasian older patients with advanced age (> or = 60) and chronic kidney disease stages 3-4. To assess the utility of prediction equations in relation to body composition, we measured lean mass (LM) with densitometry (DXA). Pearson's, Bland-Altman and Lin's coefficient (Rc) were used to study accuracy and precision. RESULTS: 51Cr-EDTA was 36.9 +/- 9.2 ml/min/1.73 m2 (22-60). Cys C levels were 2.2 +/- 0.8 mg/l (r = 0.085; p = 0.662 LM) and creatinine 2.8 +/- 1.1 mg/dl (r = 0.427; p = 0.021 LM). The most accurate equations were the Hoek, Larsson and Stevens formulae, with a bias of -0.2 (Rc 0.48), -2.9 (Rc 0.44) and 2.6 ml/min/1.73 m2 (Rc 0.58). The biases obtained with MDRD-IDMS and CG were -14.6 (Rc 0.35) and -12.5 (Rc 0.40). All correlations among biases obtained with creatinine-based formulae and LM were negative and statistically significant (p < 0.05). CONCLUSIONS: The results show superiority of Cys C-based GFR formulae over the MDRD-IDMS and CG equations. This significant underestimation obtained with conventional prediction equations was directly related to the influence of LM.

Preanalytical quality control program - an overview of results (2001-2005 summary).

BACKGROUND: Preanalytical variables, such as sample collection, handling, transport, and storage, may affect patient results. The number of errors in the preanalytical phase may decrease by following standardized procedures. METHODS: A retrospective analysis (2001-2005) of results obtained through the Spanish Society of Clinical Chemistry and Molecular Pathology Quality Assessment Program for the Preanalytical Phase has been carried out to summarize data regarding the main factors affecting the preanalytical phase quality. In such a program, participants are asked to register rejections and causes for rejection of routine or stat samples usually and locally collected at their laboratories. RESULTS: Results discussed refer to 105 laboratories. Of the 4,715,132 tubes expected to be received during the data collection period among participating laboratories and according to determinations included by clinicians in the request form, 32,977 (0.699%) offered a cause for rejection. Whole blood-EDTA samples and serum samples accounted for 75.6% of all samples collected among laboratories, although they only corresponded to 55.8% of all registered rejections. In total, 81% of rejections arose as a result of the following reasons: "specimen not received" (37.5%), "hemolysis" (29.3%), and "clotted sample" (14.4%). Moreover, plasma-citrate-erythrocyte sedimentation rate exhibited the highest percentage of rejection (1.473%), whereas the lowest rate corresponded to whole blood-EDTA (0.381%). CONCLUSIONS: Overall percentage of rejection is similar to previously published data. As some of the included variables have turned out to be irrelevant, the program has been simplified from the year 2006 onwards.