RESUMEN
BACKGROUND: Determination of the white cell (WBC) count in WBC-reduced platelet components requires methods that have a detection limit in the range of approximately 5.0 x 10(2) to 5.0 x 10(4) per mL. STUDY DESIGN AND METHODS: With a 50-microL Nageotte hemocytometer and bright-field microscopy (200x magnification), studies were conducted to develop and validate a method that could be used routinely with filtered and apheresis-harvested platelets. A 1-in-5 dilution of sample with a commercially available blood-diluting fluid was used because, with a lower (1-in-2) dilution, the observed number of WBCs was substantially less than the number expected at relatively high platelet counts (> 1.9 x 10(9)/mL). RESULTS: The observed and expected WBC counts in WBC-reduced platelet samples correlated well at levels between approximately 5 and 1100 WBCs per counting area (5.0 x 10(2)-1.1 x 10(5)/mL). At levels of more than 300 to 400 WBCs per counting area, accurate counts were obtained when 10 of the 40 rectangles were counted. CONCLUSION: These studies provide data to confirm that the 50-microL Nageotte hemocytometer can be used to accurately count low levels of WBCs in platelet components.
Asunto(s)
Recuento de Leucocitos/instrumentación , Plaquetoferesis , Diagnóstico por Computador , Estudios de Evaluación como Asunto , Humanos , Recuento de Leucocitos/métodos , Coloración y EtiquetadoRESUMEN
Platelet concentrates (PCs) prepared from units of whole blood are routinely stored singly at 20 to 24 degrees C and pooled prior to transfusion. Studies have been conducted to evaluate the in vitro properties of pools of six (n = 19) and eight (n = 17) ABO-identical PCs after storage, with comparative studies involving single units (n = 33). The pools were prepared using the sterile connecting device. One-day-old and 3-day-old PCs were pooled and stored for a total of 5 days in a container system consisting of two 1000-mL polyolefin containers. The pooled platelet suspension was divided approximately equally between the two containers. The platelet count was reduced by less than 5 percent during storage of the pools, which is similar to the reduction found with storage of control units of single PCs. The volume loss due to pooling was 9.6 +/- 1.9 percent (mean +/- 1 SD). The pH of the PC pools was approximately 7.0 after 5 days of storage, with no pool having a pH below 6.2. In vitro platelet properties, such as morphology score, extent of shape change induced by ADP, total ATP, aggregation response to ADP and collagen, response to hypotonic stress, lactate dehydrogenase discharge, and beta-thromboglobulin release, were similar for pools and control single PCs. In addition, comparable low levels of thymidine uptake were detected in the mononuclear leukocyte fraction of pooled and unpooled PCs that were stored for 5 days at 20 to 24 degrees C, which indicates that the mixing of lymphocytes in the pool did not stimulate in vitro immunologic reactions.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Plaquetas , Conservación de la Sangre , Plaquetas/citología , Plaquetas/fisiología , Volumen Sanguíneo , Supervivencia Celular , Hemostasis , Humanos , Leucocitos Mononucleares/metabolismo , Prueba de Cultivo Mixto de Linfocitos , Timidina/farmacocinética , TritioRESUMEN
The ability of two fundamentally different photochemical procedures to inactivate model viruses in platelet suspensions was compared. Merocyanine 540 (MC 540) with visible light was used as an example of an oxygen-dependent chemical-directed at the viral membrane, and aminomethyl trimethyl psoralen (AMT) with ultraviolet A light (UVA) was used as an example of a nucleic acid-directed system. Antiviral conditions in petri dishes were identified and the effects of these procedures on platelet suspensions in plastic storage containers were studied. Concentrations of photochemicals in the 10 to 150 mumol range with 30 to 60 minutes of visible light (MC 540) or 1 to 2 minutes of UVA (AMT) readily inactivated 5 to 6 log10 of vesicular stomatitis virus (VSV) and other model viruses in platelet suspensions, provided the plasma concentration was reduced to about 15 percent by the use of a synthetic platelet storage medium. Extracellular pH, morphology scores, and aggregation response dropped markedly when platelets were treated with MC 540 and visible light. However, treatment with 136 mumol per L of AMT and 1 to 3 minutes of UVA could inactivate 5 log10 of VSV in platelet suspensions with retention of platelet characteristics for 4 days, particularly if oxygen levels were reduced during treatment. These studies demonstrate that AMT-UVA treatment meets the initial requirements for virus inactivation in platelet suspensions.