The Philadelphia LSH Study was a randomized trial that offered environmental education, evaluation, and remediation, as needed, to the families and homes of high-risk newborn children. It was conducted by workers from the Philadelphia Department of Public Health, the Children's Hospital of Philadelphia, the National Nursing Centers Consortium, St. Christopher's Hospital for Children, and Drexel University, whose institutional review boards approved the study, which was funded through a HUD Lead Technical Studies grant.
We recruited study children from urban outpatient practices located in low-income neighborhoods of Philadelphia, where the prevalence of children with elevated BLLs is higher than average. After the outreach workers explained the study and obtained informed consent from the child's caregiver, the study coordinator selected the next card in the random sequence to randomize that family to receive either standard lead-poisoning prevention education (standard education group; hereafter, SEG) or standard education with additional extensive education regarding essential maintenance practices for keeping a home in lead safe condition (maintenance education group; hereafter, MEG). The outreach workers reviewed the MEG educational points with the families at each study visit. The additional education was compiled into a 22-page handbook, which included information on the problems regarding older homes and LBP hazards and a series of tips for families, such as preventing damage to paint, looking out for peeling or chipping paint, completing the maintenance diary each month, reporting problems with LBP hazards in their homes, working safely with LBP (this involved a list of explicit actions to take to maintain safety), and a list of “dos” and “don'ts” for household cleaning. The handbook was created using information from booklets published by the U.S. Environmental Protection Agency (EPA), HUD, CDC, and the Maine Department of Environmental Protection.
We randomized blocks using computer-generated random numbers. The outreach workers educated participating families during the baseline, six-month, and 12-month home visits. Parents were given cleaning materials and supplies, and workers reinforced the prevention education (including specific cleaning instructions) during study visits. (Workers conducted the six-month educational intervention by phone for study families unable to arrange a home visit.) The study staff and health department staff (arranging LHC work) followed a detailed protocol for attempting to reach families lost to follow-up, including multiple phone and mail contacts, visits to the last known address, and contact with the subject's primary care provider.
We recruited the study children from outpatient practices of The Children's Hospital of Philadelphia, St. Christopher's Hospital for Children, and several nurse-managed health centers participating in the National Nursing Centers Consortium. A comparison group, with a 2:1 match, was identified from The Children's Hospital of Philadelphia clinical database, and controls were matched by age, census tract, racial/ethnic background, and gender. Eight children could not be matched on racial/ethnic background but were matched for the other characteristics. We created the comparison group to compare the BLLs of children receiving one of the study interventions with those who had received the community standard for prevention of elevated BLLs, such as information from the child's health-care provider during clinical visits. We utilized an electronic recruitment tool that was managed by the Pediatric Research Consortium for The Children's Hospital of Philadelphia practices. Families were asked if someone could call them about the study, and a list of interested parents was regularly relayed to study staff. Other children were identified through wall posters and direct referral from health-care providers. Eligible children resided in Philadelphia County, spoke either English or Spanish, had a home that was judged to be in a condition enabling remediation (in stable condition), and did not have a history of elevated BLLs. The outreach worker team included a bilingual worker, and all documents were translated into Spanish. We excluded families if they had participated in the Lead Safe Babies program or received services from the Childhood Lead Poisoning Prevention Program of the Philadelphia Department of Public Health for other children in the family.
The study team formed a community advisory board, which comprised representatives from the targeted community, and met regularly following recommendations detailed in the National Research Council's 2005 report on housing-related health hazards involving children.24
Parental knowledge assessment
All families were administered pre- and posttests with both standard lead and maintenance questions on the first home visit (before and after the education was given), and the standard lead test was repeated at six and 12 months. The maintenance posttest was also administered to MEG families at these visits. The study utilized the shortened version of the Chicago Lead Knowledge Test,25
modified by Hans Kersten.26
The test evaluates parental knowledge regarding lead exposure prevention. Test-retest reliability of the full Chicago Lead Knowledge Test was 0.96 but has not been assessed for the shortened version. The SEG test had 14 questions, and possible scores ranged from 1 to 14, with one point scored for each correctly answered question. The MEG test was similar, except it had only 10 questions, with a possible score ranging from 1 to 10.
Quality control measures
Per HUD specifications, we formulated a quality assurance plan detailing the protocols and quality assurance procedures to be used for specimen (lead dust) and data collection. BLLs were drawn by each subject's primary care provider, and results were reported to study staff.
Collection of study data
Data verification procedures were in place to ensure accuracy of data collection and data entry. The study manager entered data into a Microsoft® Excel database. The study manager and principal investigator routinely performed quality assurance evaluations on selected study charts to identify errors in data entry. Following completion of data cleaning and quality assurance procedures, the data was imported into a statistical software program, SPSS® version 18,27
The outreach workers systematically evaluated each subject's residence by looking at the condition of paint (intact, fair, or poor) and testing for lead dust levels at baseline and at 12 months. Areas judged to be fair had a paint defect or visible dust on ≤10 square feet (sq ft) of exterior surfaces, ≤2 sq ft of interior surfaces, or less than 10% of small surfaces. Areas were labeled as poor if these limits were exceeded. Homes were reassessed whenever a subject moved.
Collection of lead dust specimens
Study personnel trained by a certified risk assessor, in accordance with EPA and HUD protocols, uniformly collected the dust wipe specimens for home evaluation. Field audits were performed. They took samples from two floor areas and one windowsill area, where the infant was likely to spend the most time during the first year. Measured areas of the floor (1 sq ft) and windowsill (variable area) were sampled with a standard pre-wetted towelette.
Field blank and spiked specimens were submitted regularly. Specimens were initially analyzed by the International Asbestos Testing Laboratory of Mount Laurel, New Jersey, and then by EMSL of Westmont, New Jersey, both of which are National Lead Laboratory Accreditation Program-certified laboratories for dust wipe analysis. Clearance dust wipes, including a full set of 13 wipes, were collected after environmental remediation, per HUD protocol, with homes re-cleaned until all clearance levels were below EPA standards.
Home remediation/LHC work
We offered LHC work for homes that had either an elevation of any of the three lead dust levels above EPA standards (>40 μg/sq ft for floors and >250 μg/sq ft for windowsills) or visual evaluation results showing at least one area in poor or at least two areas in fair condition at either the baseline or 12-month home evaluation. A small number of homes meeting criteria for referral were not referred, due to minimal areas of concern on visual inspection and the high numbers of homes meeting criteria for this work. Once referred, health department abatement staff evaluated the property and specified the LHC work, including paint stabilization and replacement of deteriorated building components when needed, repainting, and specialized lead dust cleaning (known as a Superclean). Services were rendered by Pennsylvania-certified Phildelphia Public Health Department abatement staff members or lead abatement contractors, per HUD guidelines.28
All homes receiving remediation also received a Superclean. The MEG families were also asked to assess their homes monthly for needed repair or maintenance work, such as deterioration of the paint or presence of water leaks, by use of a special diary, and these families were referred to Childhood Lead Poisoning Prevention Program staff in the same manner. During contacts with the families by phone at one, three, and nine months from enrollment and in person during home visits at six and 12 months, the outreach workers questioned MEG families about identification of new areas noted to need repair or maintenance work.
The results of the environmental evaluation and dust wipe testing were reported within several weeks by letter to the parent/guardian and the property owner. For houses with an identified lead problem, the letter indicated that the home would need to be further checked and some type of remediation work would be required, which could be provided by study staff at no charge.
Blood lead testing (in most cases, venous) was carried out by the subject's primary care provider and employed the services of five different laboratories, all of which participated in at least one proficiency program for BLL analysis. All of the study children's providers were encouraged to do blood lead screening of their patients using the high-risk protocol recommended by the Philadelphia Department of Public Health at 9–12 months, 15–18 months, 2 years, and 3 years of age. The Children's Hospital of Philadelphia clinics caring for the control children had access to general information and posted recommendations, but did not receive a specific screening protocol.
Periodic cleaning summary
Outreach workers assessed cleaning activity by questioning the parent at the baseline, six-month, and 12-month home visits. We tabulated results for wet dusting and mopping of the subject child's bedroom, living room, dining room, bathroom, and hallway areas and broke them into the following categories of cleaning frequency: low (quarterly), moderate (bimonthly or monthly), or high (daily or weekly).
Study Question 1 hypothesized that study interventions would result in lower BLLs in the LSH Study cohort when compared with a group of children whose parents did not receive these interventions. We compared geometric mean BLLs (due to non-normal distribution) of the study children and a comparison group using a two-tailed t-test. Sample size calculations estimated, with an average (pooled) standard deviation of 2.5, that 256 children per group would provide 80% power to detect a mean difference of 0.6 μg/dL in BLLs.
Study Question 2 hypothesized that at least 15% fewer MEG homes would have home evaluation results meeting criteria for remediation at 12 months, compared with SEG homes, using Chi-square comparison. This analysis required a sample size of 128 per group (for both the SEG and MEG) to compare remediation rates of 30% vs. 45%, to achieve 80% power in a one-tailed test.
Study Question 3 involved calculating descriptive statistics of multiple housing variables over time. Outcomes included whether the households met criteria for home evaluation failure, referral for remediation work, cleaning frequency, and cost of remediation. We performed two different analyses to compare percentages regarding housing characteristics. A Chi-square test compared the percentages for all children with data at each visit, as if they were two independent groups. This approach maximized the sample size, since only one-third of the sample had data at 12 months. We performed a McNemar's test on the study children with data at both visits. This approach compares subjects to themselves, providing a cleaner comparison, but excludes most of the baseline data.
Study Question 4 determined significant predictors of BLL by using bivariate tests such as Mann-Whitney U tests and t-tests (for dichotomous variables), analysis of variance (multiple groups), and correlation coefficients (numeric variables). Key child, family and household, home assessment, study arm, and test-score characteristics were evaluated.
Study Question 5 hypothesized that parents receiving lead education would increase their general lead knowledge at baseline and retain this over time, and the MEG would score higher on the standard lead test than the SEG. We used two-tailed Wilcoxon tests to determine changes from baseline within groups and Mann-Whitney U tests to compare groups at each visit. A Spearman correlation was used to test for association (hypothesized to be negative) between parental knowledge at 12 months and 12-month BLLs. This correlation was assessed separately for the two groups. With 128 children per group, the study had adequate power (80%) to detect correlations as small as 0.3.