Letters to the Editor
et.al. NEJM 307:573-579 (1982); MMWR 46:141-146 (1997)]. For example, lead additives are no longer used in gasoline, lead paints are banned from use on residential buildings (although old paint still remains), lead solders are no longer used on water pipes or food cans, plumbing fixtures are largely lead-free, and industries using lead have made significant progress in limiting worker exposures.Twenty years ago, blood leads up to 20
g/dL reflected unavoidable environmental exposure by children or adults. More than a decade ago we lowered our normal range for both children and adults to <10 g/dL, a level that coincides with Centers for Disease Control guidance [see Preventing Lead Poisoning in Young Children (Atlanta: CDC, October 1991); Screening Young Children for Lead Poisoning (Atlanta: CDC, November 1997); Case Studies in Environmental Medicine: Lead Toxicity (Atlanta, CDC, May 2000)].Blood leads less than 10
g/dL reflect what is actually seen in individuals (both adults and children) who do not have any extraordinary source of lead exposure. Test findings do not vary appreciably between methodologies as long as necessary precautions are taken to prevent analytical contamination. For children whose levels are between 10 and 20
g/dL, parental counseling and environmental dust suppression are advised. Clinical evaluation is essential for children whose levels are greater than 20
g/dL, and at somewhat higher levels pediatricians may decide upon intervention
(chelation therapy). A blood lead of 45 g/dL or higher in a child is considered a medical emergency.Adult workers can tolerate higher blood lead levels, and here interpretation is guided by OSHA standards. Generally, levels up to 40
g/dL are considered acceptable in a factory setting, while workers whose level exceeds 50
g/dL need to be removed from further exposure. In current practice, companies where exposures are high institute environmental and work practice controls to maintain worker levels well beneath 40
g/dL. At many such firms, the average blood lead today is only 20 or 25
g/dL.Routine blood lead monitoring, along with physician vigilance, is our primary line of defense against lead poisoning for both children and adults. A child whose initial screen yields a blood lead greater than 9
g/dL should have a venous confirmation as soon as possible to rule out specimen contamination, and then be studied to determine the probable source of the exposure, prevented from further exposure, and followed carefully by a pediatrician. Likewise, adults with elevated levels need to be monitored to assure that levels remain within a safe range and that signs or symptoms of lead toxicity do not appear.I recommend that you revise your blood lead reference interval to less than10
/dL (applying to both children and adults) to coincide with current federal guidance.Leon A.
Saryan, Ph.D.
Technical Director
ACL Industrial Toxicology Laboratory
Aurora Health Care
Milwaukee, WIEditors note: The CDC recently published an article in Morbidity and Mortality Weekly Report (MMWR), available online atwww.cdc.gov/mmwr/preview/mmwrhtml/mm4950a3.htm, that included data from the 1999 Report for children 1 to 5 years old and additional state and local surveillance data for elevated blood lead levels among children. The article notes that although blood lead levels are dropping in these children when considered as a group, elevated blood lead levels among children continue to be a major public health concern.Because of leads adverse effects on cognitive development, CDC has defined an elevated blood lead level as >10
g/dL for children younger than 6 years of age. Data from CDCs Third National Health and Nutrition Examination Survey
(NHANES), Phase 2 (1991-1994) showed that the geometric mean blood lead level for children 1 to 5 years of old was 2.7 micrograms per deciliter
(g/dL) (95 percent confidence interval 2.5-3.0 g/dL). Results in the report for the same age group for 1999 show that the geometric mean blood lead level has decreased to 2.0
g/dL (95 percent confidence interval 1.7-2.3 g/dL). The sample size in the report for 1999 is too small to provide reliable estimates of the percentage of children with blood lead levels >10
g/dL. In future releases of the report, more blood lead data will be available for this age group, thus permitting reliable estimates of the percentage of children with elevated blood lead levels.Thank you for recognizing cytotechnologistsI appreciate that you have published an article with a cytotechnologist as a co-author (The Complaint Department How does a lab properly investigate a problem? December 2001). Often cytotechnologists are ignored when general laboratory aspects are discussed. CTs are considered too specialized to have problems in common with other
laboratorians, or they are not considered at all. I expect that Rita
Vivero, MBA, CT(ASCP) has experienced some of the same difficulties with specimen collection and delivery, and report issuance and receipt as her colleagues have, and was a valuable collaborator in the systems approach to solving complaints described in the article.Roberta M.
Goodell, CFIAC, CT(ASCP)
Searsmont, ME©
2002 Nelson Publishing, Inc. All rights reserved.
Readers Respond
Recommends blood lead level reference interval revisionI am writing to comment on the reference interval for blood lead published on page 14 of your 2001-2002 CLR (Clinical Laboratory Reference). While I realize that a one-page table of reference values cannot provide complete information needed for test interpretation, I do believe that the value provided for lead (<50 g/dL) is misleading and could result in an unsatisfactory outcome, especially for a child affected by lead exposure.Our laboratory is one of the leading laboratories in the country specializing in lead testing. Our patient population includes adult workers, (especially those who sustain lead exposure at the workplace), as well as children. We have clients in almost every state and several foreign countries. Currently, our blood lead volume exceeds 60,000 tests annually.In arriving at a reference or normal range for blood lead, we considered first of all that lead is essentially an environmental contaminant that is neither synthesized by living organisms nor of any demonstrated essentiality in human biochemistry. Over the past two decades, blood lead levels have decreased in the American population as various uses of the metal have been limited or curtailed [see KR Mahaffey,et.al. NEJM 307:573-579 (1982); MMWR 46:141-146 (1997)]. For example, lead additives are no longer used in gasoline, lead paints are banned from use on residential buildings (although old paint still remains), lead solders are no longer used on water pipes or food cans, plumbing fixtures are largely lead-free, and industries using lead have made significant progress in limiting worker exposures.Twenty years ago, blood leads up to 20
g/dL reflected unavoidable environmental exposure by children or adults. More than a decade ago we lowered our normal range for both children and adults to <10 g/dL, a level that coincides with Centers for Disease Control guidance [see Preventing Lead Poisoning in Young Children (Atlanta: CDC, October 1991); Screening Young Children for Lead Poisoning (Atlanta: CDC, November 1997); Case Studies in Environmental Medicine: Lead Toxicity (Atlanta, CDC, May 2000)].Blood leads less than 10
g/dL reflect what is actually seen in individuals (both adults and children) who do not have any extraordinary source of lead exposure. Test findings do not vary appreciably between methodologies as long as necessary precautions are taken to prevent analytical contamination. For children whose levels are between 10 and 20
g/dL, parental counseling and environmental dust suppression are advised. Clinical evaluation is essential for children whose levels are greater than 20
g/dL, and at somewhat higher levels pediatricians may decide upon intervention
(chelation therapy). A blood lead of 45 g/dL or higher in a child is considered a medical emergency.Adult workers can tolerate higher blood lead levels, and here interpretation is guided by OSHA standards. Generally, levels up to 40
g/dL are considered acceptable in a factory setting, while workers whose level exceeds 50
g/dL need to be removed from further exposure. In current practice, companies where exposures are high institute environmental and work practice controls to maintain worker levels well beneath 40
g/dL. At many such firms, the average blood lead today is only 20 or 25
g/dL.Routine blood lead monitoring, along with physician vigilance, is our primary line of defense against lead poisoning for both children and adults. A child whose initial screen yields a blood lead greater than 9
g/dL should have a venous confirmation as soon as possible to rule out specimen contamination, and then be studied to determine the probable source of the exposure, prevented from further exposure, and followed carefully by a pediatrician. Likewise, adults with elevated levels need to be monitored to assure that levels remain within a safe range and that signs or symptoms of lead toxicity do not appear.I recommend that you revise your blood lead reference interval to less than10
/dL (applying to both children and adults) to coincide with current federal guidance.Leon A.
Saryan, Ph.D.
Technical Director
ACL Industrial Toxicology Laboratory
Aurora Health Care
Milwaukee, WIEditors note: The CDC recently published an article in Morbidity and Mortality Weekly Report (MMWR), available online atwww.cdc.gov/mmwr/preview/mmwrhtml/mm4950a3.htm, that included data from the 1999 Report for children 1 to 5 years old and additional state and local surveillance data for elevated blood lead levels among children. The article notes that although blood lead levels are dropping in these children when considered as a group, elevated blood lead levels among children continue to be a major public health concern.Because of leads adverse effects on cognitive development, CDC has defined an elevated blood lead level as >10
g/dL for children younger than 6 years of age. Data from CDCs Third National Health and Nutrition Examination Survey
(NHANES), Phase 2 (1991-1994) showed that the geometric mean blood lead level for children 1 to 5 years of old was 2.7 micrograms per deciliter
(g/dL) (95 percent confidence interval 2.5-3.0 g/dL). Results in the report for the same age group for 1999 show that the geometric mean blood lead level has decreased to 2.0
g/dL (95 percent confidence interval 1.7-2.3 g/dL). The sample size in the report for 1999 is too small to provide reliable estimates of the percentage of children with blood lead levels >10
g/dL. In future releases of the report, more blood lead data will be available for this age group, thus permitting reliable estimates of the percentage of children with elevated blood lead levels.Thank you for recognizing cytotechnologistsI appreciate that you have published an article with a cytotechnologist as a co-author (The Complaint Department How does a lab properly investigate a problem? December 2001). Often cytotechnologists are ignored when general laboratory aspects are discussed. CTs are considered too specialized to have problems in common with other
laboratorians, or they are not considered at all. I expect that Rita
Vivero, MBA, CT(ASCP) has experienced some of the same difficulties with specimen collection and delivery, and report issuance and receipt as her colleagues have, and was a valuable collaborator in the systems approach to solving complaints described in the article.Roberta M.
Goodell, CFIAC, CT(ASCP)
Searsmont, ME©
2002 Nelson Publishing, Inc. All rights reserved.
