Robert C. Blaylock

Anucleate platelets generate progeny

Platelets are classified as terminally differentiated cells that are incapable of cellular division. However, we observe that anucleate human platelets, either maintained in suspension culture or captured in microdrops, give rise to new cell bodies packed with respiring mitochondria and alpha-granules. Platelet progeny formation also occurs in whole blood cultures. Newly formed platelets are structurally indistinguishable from normal platelets, are able to adhere and spread on extracellular matrix, and display normal signal-dependent expression of surface P-selectin and annexin V. Platelet progeny formation is accompanied by increases in biomass, cellular protein levels, and protein synthesis in expanding populations. Platelet numbers also increase during ex vivo storage. These observations indicate that platelets have a previously unrecognized capacity for producing functional progeny, which involves a form of cell division that does not require a nucleus. Because this new function of platelets occurs outside of the bone marrow milieu, it raises the possibility that thrombopoiesis continues in the bloodstream.

The utility of patient characteristics in predicting severe ADAMTS13 deficiency and response to plasma exchange

BACKGROUND: Idiopathic thrombotic thrombocytopenic purpura (TTP) is a rare form of thrombotic microangiopathy (TMA) characterized by extreme deficiency of ADAMTS13, an enzyme responsible for cleavage of von Willebrand factor. Plasma exchange therapy is the cornerstone of current treatment and is ineffective for most other forms of TMA. The availability of ADAMTS13 testing has improved diagnostic accuracy and appropriate selection of patients who are most likely to respond to plasma exchange.

Bacteria differentially induce degradation of Bcl-xL, a survival protein, by human platelets.

Bacteria can enter the bloodstream in response to infectious insults. Bacteremia elicits several immune and clinical complications, including thrombocytopenia. A primary cause of thrombocytopenia is shortened survival of platelets. We demonstrate that pathogenic bacteria induce apoptotic events in platelets that include calpain-mediated degradation of Bcl-x(L), an essential regulator of platelet survival. Specifically, bloodstream bacterial isolates from patients with sepsis induce lateral condensation of actin, impair mitochondrial membrane potential, and degrade Bcl-x(L) protein in platelets. Bcl-x(L) protein degradation is enhanced when platelets are exposed to pathogenic Escherichia coli that produce the pore-forming toxin α-hemolysin, a response that is markedly attenuated when the gene is deleted from E coli. We also found that nonpathogenic E coli gain degrading activity when they are forced to express α-hemolysin. Like α-hemolysin, purified α-toxin readily degrades Bcl-x(L) protein in platelets, as do clinical Staphylococcus aureus isolates that produce α-toxin. Inhibition of calpain activity, but not the proteasome, rescues Bcl-x(L) protein degradation in platelets coincubated with pathogenic E coli including α-hemolysin producing strains. This is the first evidence that pathogenic bacteria can trigger activation of the platelet intrinsic apoptosis program and our results suggest a new mechanism by which bacterial pathogens might cause thrombocytopenia in patients with bloodstream infections.

Teaching pediatric laboratory medicine to pathology residents

CONTEXT Laboratory data are essential to the medical care of fetuses, infants, children, and adolescents. However, the performance and interpretation of laboratory tests on specimens from these patients, which may constitute a significant component of the workload in general hospitals and integrated health care systems as well as specialized perinatal or pediatric centers, present unique challenges to the clinical pathologist and the laboratory. Therefore, pathology residents should receive training in pediatric laboratory medicine. OBJECTIVE Childrens Health Improvement through Laboratory Diagnostics, a group of pathologists and laboratory scientists with interest and expertise in pediatric laboratory medicine, convened a task force to develop a list of curriculum topics, key resources, and training experiences in pediatric laboratory medicine for trainees in anatomic and clinical pathology or straight clinical pathology residency programs and in pediatric pathology fellowship programs. DATA SOURCES Based on the experiences of 11 training programs, we have compiled a comprehensive list of pediatric topics in the areas of clinical chemistry, endocrinology, hematology, urinalysis, coagulation medicine, transfusion medicine, immunology, microbiology and virology, biochemical genetics, cytogenetics and molecular diagnostics, point of care testing, and laboratory management. This report also includes recommendations for training experiences and a list of key texts and other resources in pediatric laboratory medicine. CONCLUSIONS Clinical pathologists should be trained to meet the laboratory medicine needs of pediatric patients and to assist the clinicians caring for these patients with the selection and interpretation of laboratory studies. This review helps program directors tailor their curricula to more effectively provide this training.

Intravenous immune globulin therapy for Stevens-Johnson syndrome/toxic epidermal necrolysis complicated by hemolysis leading to pigment nephropathy and hemodialysis

BACKGROUND Intravenous immune globulin (IVIG) is generally thought to be of relatively low risk for adverse events and some experts consider this to be the best treatment for Stevens-Johnson syndrome/toxic epidermal necrolysis. OBJECTIVE We evaluated the underlying cause of anemia and renal failure in 2 consecutive patients being treated with IVIG for Stevens-Johnson syndrome/toxic epidermal necrolysis. METHODS This is a retrospective chart review. RESULTS We present 2 patients with Stevens-Johnson syndrome/toxic epidermal necrolysis and severe hemolysis requiring blood transfusion who subsequently developed pigment nephropathy necessitating hemodialysis after treatment with IVIG. Both patients had antibodies to their ABO blood type detected in the eluate from their red blood cell membrane. LIMITATIONS This is a retrospective review with only 2 cases. CONCLUSIONS We propose that IVIG-associated hemolysis is an adverse reaction that may not be as rare as once thought, presenting as a mild decrease in hemoglobin and hematocrit. Antibodies to blood type A and B are given as part of pooled immune globulin and are considered to be the cause of hemolysis. More severe anemia requiring transfusion is less common, and the breakdown products produced by hemolysis can lead to pigment nephropathy and renal failure. We present methods by which this severe complication can be anticipated and managed more effectively.

Quality Improvement After Multiple Fatal Transfusion-Transmitted Bacterial Infections

Objectives Transfusion-transmitted bacterial infection (TTBI) from platelet components is likely underrecognized and can be fatal. Twenty-four-hour prospective culture was felt to be insufficiently preventive after multiple TTBIs occurred and strategies to improve safety were sought. Methods Two fatal and one severe TTBIs occurred from a split-apheresis platelet donation contaminated with Klebsiella pneumoniae. Improvement opportunities were identified and corrective and preventive action (CAPA) followed. Results To mitigate bacterial contamination and improve detection sensitivity, additional prospective culture 48 hours postcollection was implemented. Since implementation, secondary cultures have caught two true positives (0.01%) missed by 24-hour culture. Bacterial testing at issue and pathogen reduction were later implemented as an added layer of safety. Conclusion While rare, TTBI is a prominent cause of morbidity and mortality from contaminated platelets. The approach to CAPA presented here may lower the risk of future transfusion-transmitted infections but must be weighed against potential added costs.

Managing transfusion service quality.

CONTEXT Providing blood products for transfusions is a complex process subject to errors both within and outside the transfusion service. Transfusion-related errors can have grave consequences for the patient undergoing transfusion. As with many processes performed within health care systems, there is an expectation of error-free practice. Although this is an unobtainable goal, a focused quality-management plan, employing a medical event reporting system in a just working environment, can effect measurable system-quality improvement. OBJECTIVE To illustrate the intrinsic value of quality-improvement activities through discussion of examples of quality misadventures from our transfusion service during the past 20 years. DATA SOURCES Examples of quality-improvement activities were extracted from our quality-system archives. The published literature on transfusion quality was reviewed. CONCLUSIONS Active reporting, structured investigation, and systematic resolution of transfusion-related errors are effective methods for improving and maintaining transfusion quality.