Jeffrey A. Lybarger

Monoclonal B-cell lymphocytosis as a biomarker in environmental health studies

The first studies of monoclonal B‐cell lymphocytosis (MBL) in the general population were conducted as part of environmental health investigations that began in 1991. MBL was observed as an unexpected finding when blood samples were immunophenotyped by two‐colour flow cytometric methods in common use at that time. The initial observations led to a workshop in 1995, at which case definitions were considered and medical follow‐up investigations were recommended. Medical follow‐ups were conducted in 1997 and 2003. A total of eight cases of confirmed MBL and three cases of presumptive MBL were identified. This review summarizes the findings from those investigations and discusses the issues related to using MBL as a biomarker in environmental health research and population‐based studies.

Criteria for progressive modification of neurobehavioral batteries

Six specific issues affecting the progressive modification of neurobehavioral test batteries used in field studies of populations exposed to neurotoxicants are discussed and test review recommendations are provided addressing each issue. The issues include: (a) general test review standards, (b) comprehensive assessment, (c) tailored batteries, (d) incorporation of new tests and techniques, (e) personnel and mechanisms for review, and (f) development of a battery assessing peripheral nervous system function.

Selective approaches to basic neurobehavioral testing of children in environmental health studies

To identify neurotoxic effects in children living near hazardous waste sites, the Agency for Toxic Substances and Disease Registry (ATSDR) has designed a basic Pediatric Environmental Neurobehavioral Test Battery (PENTB) for children 1 through 16 years of age. It emphasizes tests appropriate to the stages of a childs development. These stages were fundamental factors in selecting tests for the PENTB, which includes both informant- and performance-based assessment procedures. Assessment of children under 4 years of age is restricted to four informant-based instruments, to evaluate as many functions as possible while minimizing testing time and the professional expertise needed in the test setting. The assessment of children 4 through 16 years of age includes 10 performance-based tests to evaluate key functions within the cognitive, motor, and sensory domains analogous to functions affected by neurotoxic chemicals in adults. In all age groups, it is crucial to also assess family, cultural, economic, and other potentially confounding variables.

Adoption of an adult environmental neurobehavioral test battery

Nationally recognized experts participated in a 3-day workshop to discuss the complex issues associated with neurobehavioral testing in environmental health settings, and to propose basic and focused test batteries for use in evaluating populations living near hazardous chemical sites. The Adult Environmental Neurobehavioral Test Battery (AENTB), which evaluates major neurobehavioral domains and functions, was adopted by the Agency for Toxic Substances and Disease Registry (ATSDR) for use as a basic screening panel in field studies. Pilot testing of the AENTB demonstrated an examiner training requirement of 3-6 practice sessions, a mean total testing time of 58.0 min (SD = 9.6), and, for 9 of the component tests, a sample size requirement of fewer than 140 (alpha = 0.05, 95% power) to detect a 20% difference between study groups. ATSDR administered the AENTB to 467 persons, selected randomly from 1,382 participants in field study sites in three states. Total testing time varied noticeably by participant age and study site, suggesting an ongoing need for site-specific controls in each field study using the AENTB. Also planned is adoption of a pediatric test battery to evaluate the domains and functions most relevant at major stages of child development.