Effect of Multiple Freeze-Thaw Cycles on Detection of Measles, Mumps, and Rubella Virus Antibodies

We investigated the effect of multiple freeze-thaw cycles on mumps, measles, and rubella virus serum antibody levels with whole-virus immunoglobulin G enzyme-linked immunoassays. Fresh serum samples from nine healthy adult volunteers were divided into six sets of five aliquots each. Samples were taken through a total of 10 freeze-thaw cycles and stored at 4°C until assayed. Each assay measurement was done in replicates of five, and the mean value was reported. After completing 10 freeze-thaw cycles, we found no clinically or statistically significant effect on measured antibody levels and found no discernible detrimental effect on the ability to measure these antibodies by enzyme-linked immunoassays.     

HLA-DR expression in macaque neuroendothelial cells in vitro and during SIV encephalitis

HLA-DR expression in neuroendothelial cells (NEC) was studied during the course of SIV encephalitis in rhesus monkeys. HLA-DR determinants were detected on NEC in monkeys with SIV encephalitis, but not in control animals. In situ hybridization with an SIV probe indicated that HLA-DR expression was not a consequence of SIV replication within NEC. Cultured rhesus NEC stimulated with gamma interferon expressed HLA-DR to a higher degree than cultured brain fibroblasts or astrocytes. These data support the contention that NEC participate in retrovirus-induced inflammation and autoimmunity within the central nervous system.     

Gene conversion is a likely cause of mutation in PKD1

Approximately 70% of the gene responsible for the most common form of autosomal dominant polycystic kidney disease ( PKD1 ) is replicated in several highly homologous copies located more proximally on chromosome 16. We recently have described a novel technique for mutation detection in the duplicated region of PKD1 that circumvents the difficulties posed by these homologs. We have used this method to identify two patients with a nearly identical cluster of base pair substitutions in exon 23. Since pseudogenes are known to be reservoirs for mutation via gene conversion events for a number of other diseases, we decided to test whether these sequence differences in PKD1 could have arisen as a result of this mechanism. Using changes in restriction digest patterns, we were able to show that these sequence substitutions are also present in N23HA, a rodent-human somatic cell hybrid that contains only the PKD1 homologs. Moreover, these changes were also detected in total DNA from several affected and unaffected individuals that did not harbor this mutation in their PKD1 gene copy. This is the first example of gene conversion in PKD1 , and our findings highlight the importance of using gene-specific reagents in defining PKD1 mutations.      

A comparison of infusion devices at 1 ml/hr

Delivery of medications by some infusion devices is irregular. This study investigated instantaneous flow in several infusion devices set at a rate of 1 ml/hr. The following devices were tested: Infusion Pumps: IMED 956A, IVAC 570, IVION "Kids Pump." Syringe Pumps: Medfusion, Baxter, Baxter OR. Tests were performed using a Bio-Tek Infusion Device Analyzer (Model IDA-1). Instantaneous flow rate was defined as Q1/T1 where: Q=sample volume and T=time required to deliver sample volume. The infusion devices were received directly from their respective manufacturers and had not seen clinical service before testing. The units were fully charged and were tested while on AC power. The tests were conducted by the authors, using standard infusion sets and commercially prepared 5% dextrose and 0.45% sodium chloride solution. Each pump was tested for several hours and multiple trials were performed on each pump. The infusion pumps, IMED, IVION, and IVAC all demonstrated deviations from the desired flow rate. The IVAC pump had a greater fluctuation in flow from the set value of 1 ml/hr (p less than 0.02). Variances from mean +/- standard error for each device are shown in parenthesis. IMED 965A (0.005+/-0.014), IVION Kid's Pump (0.002+/-0.009), IVAC 570 (0.001+/-0.006). The Baxter syringe pump (0.002+/-0.009) also had a wide variance in flow. The Baxter OR (0.001+/-0.005) and the Medfusion (0.001+/-0.008) syringe pumps maintained the most consistent flow and showed less variance than the other devices tested.(ABSTRACT TRUNCATED AT 250 WORDS)     

A stochastic model of acute-care decisions based on patient and provider heterogeneity

The primary cause of preventable death in many hospitals is the failure to recognize and/or rescue patients from acute physiologic deterioration (APD). APD affects all hospitalized patients, potentially causing cardiac arrest and death. Identifying APD is difficult, and response timing is critical - delays in response represent a significant and modifiable patient safety issue. Hospitals have instituted rapid response systems or teams (RRT) to provide timely critical care for APD, with thresholds that trigger the involvement of critical care expertise. The National Early Warning Score (NEWS) was developed to define these thresholds. However, current triggers are inconsistent and ignore patient-specific factors. Further, acute care is delivered by providers with different clinical experience, resulting in quality-of-care variation. This article documents a semi-Markov decision process model of APD that incorporates patient and provider heterogeneity. The model allows for stochastically changing health states, while determining patient subpopulation-specific RRT-activation thresholds. The objective function minimizes the total time associated with patient deterioration and stabilization; and the relative values of nursing and RRT times can be modified. A case study from January 2011 to December 2012 identified six subpopulations. RRT activation was optimal for patients in “slightly concerning” health states (NEWS?>?0) for all subpopulations, except surgical patients with low risk of deterioration for whom RRT was activated in “concerning” states (NEWS?>?4). Clustering methods identified provider clusters considering RRT-activation preferences and estimation of stabilization-related resource needs. Providers with conservative resource estimates preferred waiting over activating RRT. This study provides simple practical rules for personalized acute care delivery.