Background aims The Quantum® Cell Expansion System (Quantum; Terumo BCT, Inc, Lakewood, CO, USA) is a novel hollow fiber-based device that automates and closes the cell culture process, reducing labor intensive tasks such as manual cell culture feeding and harvesting. The manual cell selection and expansion processes for the production of clinical-scale quantities of bone marrow-derived human mesenchymal stromal cells (BM-hMSCs) have been successfully translated onto the Quantum platform previously. The formerly static, manual, in vitro process performed primarily on tissue culture polystyrene substrates may raise the question of whether BM-hMSCs cultured on a hollow fiber platform yields comparable cell quality. Methods A rigorous battery of assays was used to determine the genetic stability of BM-hMSCs selected and produced with the Quantum. In this study, genetic stability was determined by assessing spectral karyotype, micronucleus formation and tumorigenicity to resolve chromosomal aberrations in the stem cell population. Cell phenotype, adherent growth kinetics and tri-lineage differentiation were also evaluated. HMSC bone marrow aspirates, obtained from three approved donors, were expanded in parallel using T225 culture flasks and the Quantum. Results BM-hMSCs harvested from the Quantum demonstrated immunophenotype, morphology and tri-lineage differentiation capacity characteristics consistent with the International Society of Cell Therapy standard for hMSCs. Cell populations showed no malignant neoplastic formation in athymic mice 60 days post-transplant, no clonal chromosomal aberrations were observed and no DNA damage was found as measured by micronucleus formation. Conclusions Quantum-produced BM-hMSCs are of comparable quality and demonstrate analogous genetic stability to BM-hMSCs cultured on tissue culture polystyrene substrates.

SummaryTo report a Prothrombin Time (PT) as International Normalized Ratio in controlling oral anticoagulant therapy, the Mean Normal PT (MNPT) is required. To correct for methodological differences in performing the PT test, each laboratory should determine its own MNPT for each batch of reagent using fresh blood samples from a large number of normal individuals. This would be a laborious procedure. Two models for simplified assessment of MNPT were investigated by two laboratories in a collaborative study. According to the models, the MNPT of a new batch of reagent is calculated, using the PT of a lyophilized control plasma measured with the new batch and a reference batch, as well as the MNPT of the reference batch obtained with fresh samples. Experimental results were obtained with 19 batches of bovine thromboplastin, 4 lyophilized normal control plasmas and fresh blood samples of 40 normal individuals. The PTs of the 4 lyophilized normal control plasmas were not identical to the MNPT of the fresh normal samples and also different from each other. Therefore, the uncorrected PTs of these control plasmas cannot be used as MNPT.In general, there was good agreement between measured and calculated MNPT, although some control plasmas gave better results than others. There were no significant differences between the results obtained by both calculation models.

SummaryIn The Netherlands, a particular coagulometer method for prothrombin time (PT) determination with reduced sample and reagent volumes is used by 62% of the laboratories controlling oral anticoagulant therapy. This “micro-method” has been calibrated against the manual tilt-tube technique for PT determination by six Dutch laboratories. Each laboratory tested 20 fresh normal blood samples and 60 fresh patient blood samples using both methods with the same batch of bovine thromboplastin reagent, according to a detailed protocol. Both methods were comparable as to their precision, but PTs measured by the micromethod were significantly prolonged (p <0.001, Student’s t-test) as compared to the manual method. This effect is stronger for samples of normal subjects than for patients’ samples. It was assumed that the International Sensitivity Index (ISI) of the bovine thromboplastin for the manual method was 1.00 in each laboratory. The ISI-values of the bovine thromboplastin for the micro-method determined by the six laboratories ranged from 1.00 to 1.07 (mean 1.03, SD 0.03). Our results indicate that any other laboratory, using this thromboplastin and the micromethod, should obtain accurate assessment of the International Normalized Ratio from their own mean normal PT and an ISI which is 3% higher than the ISI supplied by the thromboplastin manufacturer for the manual tilt-tube method.

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Aim-To compare the International Sensitivity Index (ISI) of the Thrombotest reagent used with a steel ball coagulometer (KC) to the ISI of the same reagent used with the manual (tilt tube) technique. Methods-The study was carried out by eight laboratories using their own KC instrument and method of testing. AUl laboratories used the same batch of Thrombotest to determine the clotting times of fresh blood samples from 20 local healthy volunteers and 60 patients on long term oral anticoagulant therapy. KC clotting times were plotted against manual clotting times on double logarithmic scales. Orthogonal regression lines were calculated to assess the ISI. Results-In two laboratories the ISI of the KC method was lower than that of the manual method; these differences, however, were 2% or less. In the other laboratories no clinically important differences were observed between ISI values obtained. However, the clotting times determined with the KC methods were shorter than the manual values. Conclusions-The ISI of Thrombotest determined with the KC methods was very similar to the manual value. Therefore, use of the ISI value supplied by the manufacturer without adjustment is justified. The mean normal prothrombin time, however, must be determined locally.