Lead Poisoning / Trace Elements Laboratory

Blood Lead

Lead Poisoning

Lead poisoning has been described as the number one environmental disease affecting children in the U.S. In 1991, the US Centers for Disease Control and Prevention (CDC) lowered the concentration of lead in blood considered harmful from 25 µg/dL to 10 µg/dL (1.21-0.48 µmol/L). In 1992, New York State enacted legislation that required all children to be screened at least once before entering school. Blood lead is the primary diagnostic and screening test for assessing lead exposure in children and adults.

The erythrocyte protoporphyrin (EP) test was previously the recommended screening test for lead poisoning but it is not very sensitive for detecting the low level lead exposures now believed to be harmful to children. Thus, the EP test was replaced by a direct blood lead test. However, EP is still used to assess the long-term effects of high level lead exposure, and is also used for monitoring patients receiving chelation therapy. It is also useful in diagnosing erythropoetic protoporphyria, a rare inherited disorder unrelated to lead poisoning.

Specimen Collection Protocols For Blood Lead

Two kinds of blood specimen can be analyzed for lead. Capillary blood obtained by skin puncture (i.e., a fingerstick), is easily obtained and can be used for screening purposes. However, strict adherence to a clean fingerstick collection protocol is vital if contamination errors are to be minimized. For information, please refer to the Fingerstick Collection Protocol. It is most important that the patient's hands be washed vigorously with soap and water immediately before blood is collected. A Microtainer safety lancet can be used to puncture the patient's middle or ring finger. We use a yellow (2.2 mm puncture depth) to achieve an adequate puncture and to promote good blood flow. Blood (150 - 250 µL) is collected into the "micro" tube. For diagnostic measurements or to monitor patients under medical management for lead poisoning, a venous blood sample must be used since it is much less likely to be compromised by contamination errors. Since all blood collection supplies are a potential source of contamination, special collection kits are available through our laboratory that have been checked for contamination and are certified by us as "lead free". Information on "lead free" kits and supplies is available (Analytical Testing Supplies).

Analytical Methdology

In our laboratory, we use electrothermal atomic absorption spectometry (ETAAS) to determine lead in blood. Our current blood lead method was developed initially for the Perkin Elmer 4100ZL instrumentation, which is equipped with a THGA system and longitudinal Zeeman background correction (1). It was intended to replace a long-standing Delves-cup atomic absorption method for blood lead that had been used successfully throughout the 1970's and 1980's in our Lead Poisoning Laboratory (2-4). Our ETAAS method is also used successfully with other THGA systems from Perkin Elmer (4110, Analyst 600, SIMMA 6000 etc.) Many aspects of our furnace method were already well established in the analytical literature (5-7) and these were adapted and optimized for use with the THGA system. The method was optimized using the principles associated with the Stabilized Temperature Platform Furnace concept (8) and thoroughly validated using a variety of reference materials and external PT programs. Later, it was shown that this blood lead method was transferable for use with the Perkin Elmer 3110 AAS equipped with the HGA system (9). It has also been adapted for use with furnace instrumentation from Varian, TJA and Hitachi (10). Although the method was intended primarily for use in the routine analysis of capillary and venous blood specimens received from childhood lead screening programs, it can also be used unmodified for the determination of lead in urine (11,12). The method is now the basis of an NCCLS proposed method for blood lead by furnace AAS (13).

Delves-cup Flame AAS

Zeeman Graphite Furnace AAS

References

1. Parsons PJ, Slavin W. A rapid Zeeman graphite furnace atomic absorption spectrometric method for the determination of lead in blood. Spectrochim Acta, Part B (1993) 48:925-939.
2. Delves HT. A micro-sampling method for the rapid determination of lead in blood by atomic-absorption spectrophotometry. Analyst (1970) 95:431-438.
3. Aldous KM, Mitchell DG, Ryan FJ. Computer-controlled atomic absorption spectrometer for measurement of transient atom populations. Anal Chem (1973) 45:1990-1993.
4. Mitchell DG, Aldous KM, Ryan FJ. Automated determination of blood lead levels in microsamples using a Delves cup, photon-counting, on-line computer, atomic absorption system. In: Barth D, Berlin A, Engel R, Recht P, Smeets J., eds. Environmental Health Aspects of Lead: Proceedings of an International Symposium, October 2-6, 1972, Amsterdam, Luxembourg: Commission of the European Communities (1973) 10813-11089.
5. Pruszkowska E, Carnrick GR, Slavin W. Blood lead determination with the platform-furnace technique. At Spectrosc (1983) 4:59-61.
6. Miller DT, Paschal DC, Gunter EW, Stroud PE, D' Angelo J. Determination of lead in blood using electrothermal atomization atomic-absorption spectrometry with a L'vov platform and matrix modifier. Analyst (1987) 112:1701-1704.
7. Subramanian KS. Determination of lead in blood: comparison of two graphite-furnace atomic-absorption spectrometric methods. At Spectrosc (1987) 8:7-11.
8. Slavin W, Manning DC, Carnrick GR The Stabilized Temperature Platform Furnace. At Spectrosc (1981) 2 (5):137-145.
9. Qiao H, Parsons PJ, Slavin W. Transferability of blood lead determinations by furnace atomic absorption spectrophotometry and continuum background correction. Clinical Chemistry (1995) 41:1451-1454.
10. Flajnik CE, Shrader D. Determining lead in blood: evaluating deuterium and Zeeman background correction. Am Clin Lab (1994) 13(9):45-47.
11. Parsons PJ, Slavin W. Electrothermal atomization atomic absorption spectrometry for the determination of lead in urine: results of an interlaboratory study. Spectrochim Acta, Part B (1999) 54:853-864.
12. Flajnik CE, Shrader D. Determination of lead in urine by GFAAS-Deuterium and Zeeman Background Correction. Varian AA Technical Note (1993) June:1-4.
13. National Committee for Clinical Laboratory Standards. Analytical Procedures for the Determination of Lead in Blood and Urine; Proposed Guideline, Wayne, PA. NCCLS Document C40-P (1998) 1-74.

Proficiency Testing Requirements

All clinical laboratories performing blood lead analyses in the US must participate in a CLIA-approved PT program for blood lead. Laboratories (other than physician office laboratories) in New York State, and those analyzing specimens originating from New York State, are required to have a clincial laboratory permit in the category Toxicology-Blood Lead, and must participate successfully in the New York State PT program for blood lead. Information on the blood lead proficiency testing program is available (Proficiency Testing Program) and questions on how to apply for a New York State permit should be directed to the Wadsworth Center's Clinical Laboratory Evaluation Program (CLEP), which is a part of the Division of Laboratory Quality Certification.

Reporting Requirements For Blood Lead in New York State

Under New York State law, all clinical laboratories that are certified for blood lead by the State Department of Health are required to report all blood lead test results electronically to the State Heavy Metals Registry, Center for Environmental Health. The data facilitate timely follow-up investigations by local health units, and provide a reliable database upon which to calculate state-wide and local prevalence rates for lead poisoning. The data are critical to the success of lead poisoning prevention efforts in New York State. Independently owned and operated physician offices or incorporated group practices regulated directly by HCFA, although not required to report blood lead test results, are strongly encouraged to participate in this public health program by reporting their results manually. Information about current reporting requirements, formats and forms for reporting results in hard copy form can be obtained from:

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