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Donor blood lead levels and transfusion safety in a vulnerable population

2015; Wiley; Volume: 55; Issue: 11 Linguagem: Inglês

10.1111/trf.13362

1537-2995

Nicholas Newman, Patricia M. Carey,

Mercury impact and mitigation studies

This issue of TRANSFUSION features a manuscript discussing blood lead levels (BLLs) in Hema-Quebec blood donors.1 The study group is fairly large with 3490 community-based blood donors from multiple regions, exhibiting high and low risks of exposure to lead and a range of ages. This characterization of donor variables defined which populations are more likely to have low or high BLLs. BLLs of at least 0.15 µmol/L (3 µg/dL) have been previously identified as the maximum level of lead in a blood donation that could safely be given to pediatric patients.2 The current study discovered that 15.5% of donors had BLL of at least 0.15 µmol/L (3 µg/dL). There was a discriminating difference in the levels based on sex and age primarily and other secondary factors including location of residence, education level, dwelling age, occupational and leisure activities, and smoking and alcohol intake. The authors present the question "what impact will this have on a vulnerable population?" Is there an "at-risk" population that might receive blood components from donors with elevated lead levels? Based on the public health impact of lead in children especially during the first years of life, neonates are a vulnerable population for whom lead exposure is to be avoided. Lead is a potent, irreversible neurotoxicant for which there is no reliable threshold for its effect.1, 3-5 Young children are particularly vulnerable to the neurotoxic effects of lead (e.g., direct damage to neuron synaptic development, myelin formation) because of the tremendous brain growth and development that takes place in the first few years of life. Lead moves from the blood into bone and soft tissues with slow release over time and maintains a dynamic equilibrium between these compartments. There has been a dramatic reduction in childhood BLL with the removal of lead from gasoline and the removal of lead from house paint. In many ways, this story describes a public health success. Symptomatic lead poisoning is now rare, but research over the past three decades has demonstrated the association between elevated, yet clinically unapparent BLLs in children with some long-term adverse outcomes. These include a decreased IQ, behavioral problems, academic failure, language delays, and increased risk of incarceration.5-8 Recognizing that toddlers are at the highest risk for lead ingestion, the American Academy of Pediatrics recommends lead screening for children at approximately 12 and 24 months of age or once after 24 months if not tested previously. Additionaly, recommendations from the local public health department impact local practices. As a result of research demonstrating the relationship between subclinical lead levels in children and adverse health effects, the Centers for Disease Control and Prevention (CDC) revised their guidance on what constitutes elevated BLL from 10 µg/dL (0.483 µmol/L) to a "reference level" of 5 µg/dL (0.2415 µmol/L). This level is based on the 97.5th percentile for BLL for children in the National Health and Nutrition Examination Survey (NHANES). In addition, the CDC affirmed that the emphasis should be the primary prevention of lead exposure.9 Approximately 70% of children are exposed to lead due to deteriorating lead paint in homes; the rest are exposed to a number of other sources, including occupational take-home exposures from their adult caregivers. Occupations at high risk for lead exposure include construction (particularly demolition), auto repair, metal recycling, and welding. Some hobbies such as hunting, fishing and art hobbies involving lead-containing paints or metals are also possible sources of exposure. Based on changing public health guidelines regarding lead exposure and the results of this article and others, blood transfusion is becoming recognized as a source of lead exposure and may be a significant source of exposure for very small children who receive multiple blood transfusions, such as premature infants.10 This exposure could be considerable if those units of blood came from donors with significantly elevated BLLs. These children are uniquely vulnerable because their brains will undergo a significant amount of growth and development outside of the natural environment of the womb. These premature babies are relatively iron deficient, and iron deficiency may work synergistically with lead poisoning to worsen long-term effects (lead competes with iron, zinc, and calcium when deficiencies are present). Since there is no known threshold for the ill effects of lead on the body, what level of lead in a donor's blood would be acceptable to transfuse? Should restrictions be in place for transfusions to neonates to assure that they are not receiving lead-contaminated blood? Akin to infectious disease screening, are there questions that blood donors could be asked to increase the positive predictive value of an elevated BLL? Further research needs to be done to understand better how to avoid lead exposure through transfusion of lead-contaminated donor blood. Is this a new area of concern for transfusion safety? Seventy-five percent of lead present in whole blood is in the red blood cells (RBCs). The remainder is in the plasma. If transfusion medicine comes to regard lead safety as a valid focal point, then consideration must be given to addressing how and when such testing would occur. Methods for detecting whole BLLs include atomic absorption spectrometry (flame or graphite furnace), anodic stripping voltammetry, and inductively coupled plasma-mass spectrometry.11 The costs per test range from $3.65 to $80.00 and test sensitivity is equally variable.12, 13 How would one model testing for lead in a transfusion medicine setting? Would this occur at a regional blood center or within individual transfusion services? Point-of-care screening instruments exist that could be used as part of the donor screening process. These devices are currently used for lead screening in high-risk children. Risk stratification of the target patient population would determine the proportion of the blood supply that would require testing. Disposition for adults who screen positive is another issue to consider, as public health funding for adult blood lead surveillance varies by jurisdiction. Transfusion safety is a prime directive in the provision of transfusion components along with purity and potency. The past few decades have seen many changes directed toward improving the safety of transfusions. These include increased testing for infectious agents, irradiation and leukoreduction of blood components, methods for bacterial detection and pathogen reduction, and other technologies. The current article by Delage and colleagues1 brings our attention to the potential risk to neonates posed by the transfusion of blood components with elevated lead levels. Should we begin a discussion on the topic of transfusion safety and lead being transfused to vulnerable populations? Well-designed studies involving not only donors but also transfusion recipients could help answer the question. Zubairi and colleagues10 measured the BLL in transfused RBCs in conjunction with pre- and posttransfusion levels in infants less than 30 weeks' gestational age (n = 75). They found a significant, linear relationship between the lead present in the transfusion product and the recipient posttransfusion levels. Carefully designed future studies will be needed to answer the questions posed by this article.1 Transfusion medicine has responded to previous infectious contaminants in the blood supply (human immunodeficiency virus, hepatitis B, hepatitis C) with innovation and a focus on patient safety. This newly recognized contaminant may require that same innovation and dedication to patient safety, especially for the most vulnerable transfusion recipients. The authors have disclosed no conflicts of interest. Nicholas Newman, DO, MS, FAAP1 Patricia M. Carey, MD, FCAP2 e-mail: patricia.carey@uc.edu 1Pediatrics and Environmental Health University of Cincinnati College of Medicine Pediatric Environmental Health and Lead Clinic Cincinnati Children's Hospital Medical Center 2Pathology and Laboratory Medicine University of Cincinnati College of Medicine Clinical Services, Hoxworth Blood Center UC Medical Center & Cincinnati Children's Hospital Medical Center Cincinnati, OH