Bacterial culture of apheresis platelets: a mathematical model of the residual rate of contamination based on unconfirmed positive results.

BACKGROUND: Platelet septic reactions result from low concentrations of bacteria that escape detection by quality-control BacT/ALERT™ culture testing. We estimate the contamination rate with these bacteria at the time of testing using a mathematical model. METHODS: Culture results and reported septic reactions are described for platelets collected between January 2007 and December 2011. Initial positive results with negative confirmatory cultures were reclassified assuming some of the 'unconfirmed positive results' represent collections contaminated with low-concentration, dormant bacteria. A mathematical model based on the probability of the detection of bacteria describes the upper limit of the residual rate of contamination. RESULTS: The rate of confirmed or unconfirmed positive apheresis platelet donations was 188 per million (1:5317) and 110 per million (1:9124), respectively. The rate of post-transfusion sepsis and reported fatalities per distributed component was 1:106 931 and 1:1 015 843, respectively. A linear decrease in unconfirmed positive Bacillus spp. cultures most likely reflected diminishing environmental contamination over time. The remaining unconfirmed positive results identified similar bacteria species as those associated with septic reactions. Assuming that these represent contamination of the collection with low-concentration, dormant bacteria, the model identified a residual contamination of 3524-204 per million (1:284-1:4902) for collections contaminated with 1-20 bacteria, respectively. DISCUSSION: Greater than 99·5% of collections contain no viable, aerobic bacteria in solution at the time of early culture testing. For every confirmed positive contaminated collection detected, there are at most 19 collections with low concentrations of dormant bacteria that are not readily detected by early BacT/ALERT™ culture.

Hispanic ethnicity, race and blood donation in the United States.

The aim of this study was to assess the hypothesis that blood donation rates vary with Hispanic ethnicity (family origin in Spanish-speaking countries) in addition to race in the United States. Lower blood donation rates have been reported among African Americans (AAs) compared with non-Hispanic European Americans (EAs). Adequate published reports on donation rates are not available for Hispanic Americans (HAs). Using data from a 2002 national survey, which included 4923 men and 7600 women aged 15-44 years with complete data, we tested the hypothesis using weighted bivariate and multivariate statistics. Among men aged 25-44 years, the percentage [95% confidence limits (95% CL)] with a history of blood donation since 1985 was similar at ages 25-34 years (46%, 42-49) and 35-44 years (41%, 37-45). It was highest in non-Hispanic EA (49%, 45-52%), intermediate in AA (35%, 30-40%) and lowest in HA (30%, 25-36%) (P < 0.001). Other variables significantly (P < 0.01) associated with history of blood donation in bivariate analyses were nativity (United States/other), education (<12/>or=12 years), poverty (<200%/>or=200% poverty limit) and married (yes/no). Variables that are not significantly associated were age, metropolitan residence (yes/no), receipt of public assistance (yes/no), current labour-force participation (yes/no) and religion raised. Compared with non-Hispanic EA, the adjusted odds ratios were essentially the same for Hispanics 0.66 (95% CL 0.47-0.92) and AAs 0.64 (95% CL 0.49-0.84). Only 34% of women had donated blood, but the association with race/ethnicity was similar. Similar patterns were also seen at ages 15-24 years. HAs and AAs have similar low blood donation rates compared with non-Hispanic EAs. The difference is not explained by sociodemographic variables.

Seasonal temperature variation and the rate of donor deferral for low hematocrit in the American Red Cross.

BACKGROUND: Hematocrit (Hct) values in healthy adult populations exhibit seasonal variation, with the lowest values occurring in the summer. The extent to which environmental temperature contributes to the seasonal trend in deferral rates for unacceptable Hct in the American Red Cross was further analyzed. STUDY DESIGN AND METHODS: A centralized database of donations during 2002 to 2004, constituting 24.3 million donor presentations, was further characterized. Data on mean monthly temperature in the United States were obtained for the same period from a government agency. Multivariate regression analyses were performed to determine the relationship between Hct deferral rates among blood donors and environmental temperature and donor characteristics. RESULTS: Hct deferral rates were associated with mean monthly temperature in the United States (R(2) = 0.77). The relationship between the Hct deferral rate and environmental temperature was strongest in the region of the country with the highest seasonal variation in temperature, followed by regions with intermediate and low seasonal variation in temperature, respectively. The seasonal pattern in Hct deferral rates occurred in both sexes and across all age groups, with significantly higher Hct deferral rates occurring in June through August compared to other quarters (p < 0.0007). CONCLUSION: There is a significant seasonal pattern in Hct deferral rates that is associated with environmental temperature. The relationship between Hct deferral rates and temperature is strongest in areas of the country with greater temperature variability. The effect of seasonality on Hct deferrals should be taken into account for donor counseling, recruitment, and retention efforts.

Update on HDFN: new information on long-standing controversies.

Hemolytic disease of the fetus and newborn (HDFN) results from maternal IgG antibodies that cross the placenta to the fetal circulation during gestation and cause RBC destruction and complications before birth (HDF), or anemia and hyperbilirubinemia after birth (HDN), or both. In its most severe form,HDF produces hydrops fetalis, which is characterized by total body edema, hepatosplenomegaly, and heart failure and can lead to intrauterine death. Before discovery of Rh immunoglobulin (RhIG), HDFN from anti-D was a significant cause of perinatal mortality or long-term disability. Routine administration of RhIG to D- women during pregnancy and shortly after the birth of D+ infants effectively reduced the incidence of HDFN caused by anti-D. Maternal alloimmunization to other RBC antigens in the Rh, Kell, and other blood group systems can not be routinely prevented and these antibodies can also cause HDFN. Advances in prenatal care, noninvasive monitoring, and intrauterine transfusion have improved the outlook for affected pregnancies to the extent that even hydrops fetalis can be reversed and effectively treated in many cases. This review will provide an update on the current issues in prevention and treatment of HDFN, emphasizing recent insights into long-standing controversies regarding maternal weak D phenotypes and D alloimmunization, noninvasive fetal diagnosis and monitoring of affected pregnancies, and recent treatment guidelines.

Ethylene glycol poisoning: toxicokinetic and analytical factors affecting laboratory diagnosis.

Ethylene glycol poisoning is an important toxicological problem in medical practice because early diagnosis and treatment can prevent considerable morbidity and mortality. When ingested in the form of antifreeze or other automotive products, ethylene glycol results in central nervous system depression, cardiopulmonary compromise, and renal insufficiency. Metabolism of ethylene glycol to organic acids is required for metabolic derangement and organ damage. Laboratory features of ethylene glycol poisoning include increased anion gap metabolic acidosis, increased osmolal gap, calcium oxalate crystalluria, and detectable ethylene glycol in serum. This Case Conference integrates discussion of the toxicokinetic and analytical variables that affect the laboratory diagnosis of ethylene glycol intoxication.