Feasibility of manual white blood cell counts as a predictor of neonatal sepsis in a low-resource setting

BACKGROUND

Manual white blood cell (WBC) differential counts as a predictor for neonatal sepsis development in a low-resource setting have not been thoroughly evaluated. We hypothesized that manual differentiation (specifically immature:total [I:T] neutrophil ratios) would be feasible and useful as an adjunct to predict early-onset neonatal sepsis (EONS). Secondarily, we hypothesized that vaccination with bacillus Calmette-Guérin (BCG) and oral polio vaccine (OPV) could alter WBC differential counts and thus might reduce its predictive performance.

METHODS

We performed a prospective cohort study within a randomized trial, randomizing healthy, high-risk newborns admitted to the nursery at the national hospital in Guinea-Bissau 1:1 to BCG+OPV at admission or at discharge (usual practice). Thin capillary blood films were prepared at 2 d of age in a subset of 268 neonates. WBC counts were assessed by microscopy and neonates were followed up for sepsis development within 2 weeks.

RESULTS

Ninety-eight percent (264/268) of smears provided interpretable reads. Of the 264 children, 136 had been randomized to receive BCG+OPV prior to sampling; the remaining 128 were vaccinated at discharge. The I:T ratio (average 0.017) was lower among children who did not develop clinical sepsis but did not predict sepsis (p=0.70). Only three children had an I:T ratio >0.2 (associated with a higher probability of clinical sepsis in previous studies) but did not develop sepsis. Immunization did not alter WBC composition.

CONCLUSIONS

Manual WBC differentials are feasible in low-resource settings. WBC differentials are not affected by standard newborn immunization. However, the I:T ratio had no value in predicting subsequent development of sepsis.

Educating the next frontier of transfusionists: a transfusion camp pilot program for nurse practitioners

BACKGROUND

Blood transfusion is common and potentially lifesaving but is associated with risk and overuse. Nurse practitioners (NPs) in multidisciplinary care teams are increasingly expanding their scope of practice to transfusion medicine (TM). Resources aimed at NPs are lacking, and little is known about NP TM knowledge. Thus, we developed a pilot TM curriculum for NP credentialing and assessed its impact.

METHODS

NP leads and TM directors adapted the successful Canadian Transfusion Camp for medical postgraduate trainees into a 3-day curriculum for NPs. Two modalities were used to assess the pilot: 1) a participant demographics survey and needs assessment; and 2) the validated BEST-TEST knowledge assessment exam administered before and after the course.

RESULTS

Of the 23 volunteer participants, the majority reported prescribing blood products within the last year, primarily red blood cells. Minimal opportunities to undertake continuing medical education in TM were identified. NPs often used preprinted order forms, consultation with physicians sharing care, or local fact sheets to guide transfusion; rather than TM physician consultation or guidelines. Exam scores significantly improved after the course (before, 35.2% vs. after, 50.3%; p = 0.005), suggesting average initial knowledge being below medical postgraduate trainee-level improving to postgraduate trainee level. Questions on appropriate transfusion triggers and correct recipient identification were most correctly answered; and responses to transfusion reaction questions required improvement.

CONCLUSIONS

Our needs assessment suggests that TM resources for NPs are relevant but lacking. Our initiative supports the generalizability, scalability, and effectiveness of the Transfusion Camp program. Further implementation, refinement, and future impact assessments are required.

Temporal trends in the treatment of severe traumatic hemorrhage

BACKGROUND

This study examined the evolution of damage control resuscitation (DCR) and outcomes in severe traumatic hemorrhage (STH) at a large Canadian trauma center.

METHODS

This was a retrospective cohort study of trauma patients admitted to a level 1 trauma center between 2005 and 2010, who received 10 or more units of packed red blood cells within 24 hours of admission. Demographic and clinical findings were compared between survivors and nonsurvivors.

RESULTS

Forty-five patients were included. Twenty-five percent of patients were coagulopathic at admission. Early crystalloid use declined over the study period. The mean 24-hour fresh-frozen plasma:platelets:packed red blood cells ratio was 1:1:2. Hemorrhage-related mortality was 69%. No pedestrians survived STH. A total of 1,032 blood product units were used in the first day for nonsurvivors.

CONCLUSIONS

Principles of DCR crept into clinical practice even before the implementation of a formal STH protocol. DCR appeared to reduce the intensive care unit length of stay but not mortality. STH is associated with heavy use of blood bank resources and high mortality rates. Futility of resuscitative efforts may be predictable by mechanism and early physiological markers.

Erroneous automated optical platelet counts in 1-hour post-transfusion blood samples

Thrombocytopenic patients with acute leukemia may show high post-transfusion count increments that significantly exceed the number of transfused platelets. This study demonstrates that the automated hematology analyzer Sysmex XE-2100 reports erroneously high optical platelet counts when the blood sample contains particles in the size range of platelets or smaller. Thrombocytopenic or low-normal whole blood samples were spiked with 1 mum latex beads (n = 14) to mimic contaminants under controlled conditions. Optical and impedance measurements of spiked and control samples with the Sysmex XE-2100 were compared with the Advia 120 and the manual counts. The added beads unexpectedly increased the automated optical platelet counts in the Sysmex XE-2100 and, to a lesser extent, the Advia 120 (Wilcoxon signed ranks test, P < 0.05), while the beads were not included in the impedance or the manual microscopic platelet counts. Differential interference contrast microscopy was used to investigate samples from platelet concentrates for transfusion. Platelet concentrates (32/128) were identified as possible sources for particles that were microscopically distinct from platelets but would be included in the automated optical count. Transfusion of platelet concentrates containing contaminating particles can lead to unexpectedly high post-transfusion platelet counts and misdiagnosis of thrombocytopenic patients.

Past and Future Approaches to Assess the Quality of Platelets for Transfusion

No automated test exists to routinely measure platelet quality. Currently, the short, 5-day shelf life of platelet concentrates is largely dictated by the risk associated with bacterial contamination and not by platelet quality. With the implementation of bacterial testing and pathogen inactivation, platelet quality will become the major determinant for the shelf life of platelet concentrates. However, extended use of platelet concentrates stored beyond 5 days will require quality testing. In addition, high platelet quality would be expected to result in improved clinical efficacy, determined by count increment, improved hemostasis, and lower risk for adverse reactions in recipients. No in vitro quality test has yet demonstrated a good correlation with clinical efficacy or improved hemostasis. This review focuses on those tests of platelet quality that are based on platelet morphology. These include visual inspection of swirling, microscopic morphology score, measurement of light transmission through platelet concentrates, and platelet light scattering techniques. Recently, a new test for platelet quality has been introduced that uses dynamic light scattering. The advantages and remaining challenges for dynamic light scattering before it can become a routine platelet quality test are discussed.