Last data update: Apr 18, 2025. (Total: 49119 publications since 2009)
Records 1-14 (of 14 Records) |
Query Trace: Bhatti P[original query] |
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Endophthalmitis, cutaneous nodules, and brain lesions in stem cell transplant recipient
Axell-House DB , Nagarajan P , Bhatti MM , Mehta RS , Roy S , Ali IKM , John TM . Clin Infect Dis 2023 77 (8) 1212-1215 A 46-year-old man with relapsed acute myeloid leukemia underwent his second matched related donor stem cell transplant (SCT), after fludarabine and melphalan conditioning followed by post-transplant cyclophosphamide. He engrafted on day +20. On day +27, he developed fever, sinusitis, left eyelid swelling, and right eye subconjunctival swelling (Figure 1A). He required an urgent right vitrectomy for endophthalmitis. Seven days later, he developed skin nodules on his upper and lower extremities which progressively enlarged and became more diffuse (Figure 1Band 1C). Laboratory tests showed leukopenia (white blood cell count 3.1 × 109/L), anemia (Hb 7.2 g/dL), and severe thrombocytopenia (25 × 109/L) with normal electrolytes, and normal renal and hepatic function. Blood, urine, and sputum cultures were no growth, and infectious serologies, nucleic acid, and antigen tests were negative, including for human immunodeficiency virus, syphilis, Toxoplasma, tuberculosis, cytomegalovirus, and Strongyloides. Nasal endoscopy did not demonstrate necrosis of sinus tissue, and sinus swab cultures did not grow any organisms of clinical significance. Wide excisional skin biopsies of skin lesions demonstrated a lymphohistiocytic infiltrate and panniculitis (Figure 2A) and circular structures (Figure 2B). Vitrectomy was performed for endophthalmitis, and vitreous fluid cultures had no growth. Positron emission tomography (PET) demonstrated diffuse subcutaneous foci most numerous of the lower extremities, and a left occipitotemporal focus (Figure 3A). Shortly thereafter, he developed acute encephalopathy, drowsiness, and rhythmic movements of his right arm concerning for seizures. Brain magnetic resonance imaging (MRI) demonstrated abnormalities of the left frontal gyrus, occipital lobe, parieto-occipital sulcus, and cerebellum, concerning for embolic strokes (Figure 3B). He continued to have fever and progression of skin lesions despite treatment with meropenem, vancomycin, minocycline, and amphotericin. What is the likely diagnosis? |
Availability of Adult Vaccination Services by Provider Type and Setting
Granade CJ , McCord RF , Bhatti AA , Lindley MC . Am J Prev Med 2021 60 (5) 692-700 INTRODUCTION: Knowledge regarding the benefits for adult vaccination services under Medicaid's fee-for-service arrangement is dated; little is known regarding the availability of vaccination services for adult Medicaid beneficiaries in MCO arrangements. This study evaluates the availability of provider reimbursement benefits for adult vaccination services under fee-for-service and MCO arrangements for different types of healthcare providers and settings. METHODS: A total of 43 Medicaid directors across the 50 U.S. states and the District of Columbia participated in a semistructured survey conducted from June 2018 to June 2019 (43/51). The frequency of Medicaid fee-for-service and MCO arrangements reporting reimbursement for adult vaccination services by various provider types and settings were assessed in 2019. Elements of vaccination services examined in this study were vaccine purchase, vaccine administration, and vaccination-related counseling. RESULTS: Under fee-for-service, 41 Medicaid programs reimburse primary care providers for adult vaccine purchase (41/43); fewer programs reimburse vaccine administration and vaccination-related counseling (33/43 and 30/43, respectively). Similar results were observed for obstetricians-gynecologists, nurse practitioners, and pharmacies. Although 24 fee-for-service (24/43) and 23 MCO (23/34) arrangements cover adult vaccination services in most settings, long-term care facilities have the lowest reported reimbursement eligibility. CONCLUSIONS: In most jurisdictions, vaccination services for adult Medicaid beneficiaries are available for a variety of healthcare provider types and settings under both fee-for-service and MCO arrangements. However, because provider reimbursement benefits remain inconsistent for adult vaccination counseling services and within long-term care facilities, access to adult vaccination services may be reduced for Medicaid beneficiaries who depend on these resources. |
State policies on access to vaccination services for low-income adults
Granade CJ , McCord RF , Bhatti AA , Lindley MC . JAMA Netw Open 2020 3 (4) e203316 Importance: State vaccination benefits coverage and access for adult Medicaid beneficiaries vary substantially. Multiple studies have documented lower vaccination uptake in publicly insured adults compared with privately insured adults. Objective: To evaluate adult Medicaid beneficiaries' access to adult immunization services through review of vaccination benefits coverage in Medicaid programs across the 50 states and the District of Columbia. Design, Setting, and Participants: A public domain document review with supplemental semistructured telephone survey was conducted between June 1, 2018, and June 14, 2019, to evaluate vaccination services benefits in fee-for-service and managed care organization arrangements for adult Medicaid beneficiaries in the 50 states and the District of Columbia (total, 51 Medicaid programs). Exposures: Document review of benefits coverage for adult immunization services and supplemental survey with validation of document review findings. Main Outcomes and Measures: Benefits coverage for adult Medicaid beneficiaries and reimbursement amounts for vaccine purchase and administration. Results: Public domain document review was completed for all 51 jurisdictions. Among these, 44 Medicaid programs (86%) validated document review findings and completed the survey. Only 22 Medicaid programs (43%) covered all 13 Advisory Committee on Immunization Practices-recommended adult immunizations under both fee-for-service and managed care organization arrangements. Most fee-for-service arrangements (37 of 49) reimbursed health care professionals using any of the 4 approved vaccine administration codes; however, 8 of 49 programs did not separately reimburse for vaccine administration to adult Medicaid beneficiaries. Depending on administration route, median reimbursement for adult vaccine administration ranged from $9.81 to $13.98 per dose. Median per-dose reimbursement for adult vaccine purchase was highest for 9-valent human papillomavirus vaccine ($204.87) and lowest for Haemophilus influenzae type b vaccine ($18.09). Median reimbursement was below the private sector price for 7 of the 13 included vaccines. Conclusions and Relevance: Even in programs with complete vaccination benefits coverage, reimbursement amounts to health care professionals for vaccine purchase and administration may not fully cover vaccination provision costs. Reimbursement amounts below costs may reduce incentives for health care professionals to vaccinate low-income adults and thereby limit Medicaid adult beneficiary access to vaccination. |
Chromosome Translocations and Cosmic Radiation Dose in Male U.S. Commercial Airline Pilots.
Grajewski B , Yong LC , Bertke SJ , Bhatti P , Little MP , Ramsey MJ , Tucker JD , Ward EM , Whelan EA , Sigurdson AJ , Waters MA . Aerosp Med Hum Perform 2018 89 (7) 616-625 ![]() BACKGROUND: Chromosome translocations are a biomarker of cumulative exposure to ionizing radiation. We examined the relation between the frequency of translocations and cosmic radiation dose in 83 male airline pilots. METHODS: Translocations were scored using fluorescence in situ hybridization chromosome painting. Cumulative radiation doses were estimated from individual flight records. Excess rate and log-linear Poisson regression models were evaluated. RESULTS: Pilots' estimated median cumulative absorbed dose was 15 mGy (range 4.5-38). No association was observed between translocation frequency and absorbed dose from all types of flying [rate ratio (RR) = 1.01 at 1 mGy, 95% confidence interval (CI) 0.97-1.04]. However, additional analyses of pilots' dose from only commercial flying suggested an association (RR = 1.04 at 1 mGy, 95% CI 0.97-1.13). DISCUSSION: Although this is the largest cytogenetic study of male commercial airline pilots to date of which the authors are aware, future studies will need additional highly exposed pilots to better assess the translocation-cosmic radiation relation. |
Seroprevalence of anti-polio antibodies in children from polio high risk area of Afghanistan: A cross sectional survey 2017
Hussain I , Mach O , Hamid NA , Bhatti ZS , Moore DD , Oberste MS , Khan S , Khan H , Weldon WC , Sutter RW , Bhutta ZA , Soofi SB . Vaccine 2018 36 (15) 1921-1924 BACKGROUND: Afghanistan is one of the remaining wild-poliovirus (WPV) endemic countries. We conducted a seroprevalence survey of anti-poliovirus antibodies in Kandahar Province. METHODS: Children in two age groups (6-11months and 36-48months) visiting Mirwais hospital in Kandahar for minor ailments unrelated to polio were enrolled. After obtaining informed consent, we collected venous blood and conducted neutralization assay to detect poliovirus neutralizing antibodies. RESULTS: A total of 420 children were enrolled and 409/420 (97%) were analysed. Seroprevalence to poliovirus type 1 (PV1) was 97% and 100% in the younger and older age groups respectively; it was 71% and 91% for PV2; 93% and 98% for PV3. Age group (RR=3.6, CI 95%=2.2-5.6) and place of residence outside of Kandahar city (RR=1.8, CI 95%=1.2-2.6) were found to be significant risk factors for seronegativity. CONCLUSIONS: The polio eradication program in Kandahar achieved high serological protection, especially against PV1 and PV3. Lower PV2 seroprevalence in the younger age group is a result of a withdrawal of live type 2 vaccine in 2016 and is expected. Ability to reach all children with poliovirus vaccines is a pre-requisite for achieving poliovirus eradication. |
Seroprevalence of anti-polio antibodies in children from polio high-risk areas of Pakistan: A cross-sectional survey 2015-2016
Hussain I , Mach O , Habib A , Bhatti Z , Suhag Z , Oberste MS , Weldon WC , Sutter RW , Soofi SB , Bhutta ZA . Pediatr Infect Dis J 2017 36 (9) e230-e236 BACKGROUND: Pakistan is one of the 3 remaining wild poliovirus endemic countries. We collected sera from children to assess the prevalence of poliovirus antibodies in selected high-risk areas for poliovirus transmission. METHODS: Children in 2 age groups (6-11 and 36-48 months) were randomly selected between November 2015 and March 2016 in 6 areas of Pakistan (Sindh Province: Karachi and Kashmore; Khyber Pakhtunkhwa Province: Peshawar, Bannu and Nowshera; Punjab Province: Faisalabad). After obtaining informed consent, basic demographic and vaccination history data were collected, 1 peripheral venipuncture was obtained, and assays to detect poliovirus (PV)-neutralizing antibodies were performed. RESULTS: A total of 1301 children were enrolled and had peripheral blood drawn that analyzed. Study subjects were evenly distributed among survey sites and age groups. Anti-polio seroprevalence differed significantly among geographic areas (P < 0.001); in the 6-11 months group, it ranged between 89% and 98%, 58% and 95%, and 74% and 96% for PV serotypes 1, 2 and 3, respectively; in 36-48 months group, it ranged between 99% and 100%, 95% and 100%, and 92% and 100% for PV 1, 2, and 3, respectively. Having received inactivate poliovirus vaccine, malnourishment (stunting) and educational level of parents were found to be associated with presence of anti-polio antibodies. CONCLUSION: The polio eradication program achieved overall high serologic protection; however, immunity gaps in young children in the high polio risk areas remain. These gaps enable sustained circulation of wild poliovirus type 1, and pose risk for emergence of vaccine-derived polioviruses. Focusing on the lowest socioeconomic strata of society, where malnutrition is most prevalent, could accelerate poliovirus eradication. |
Effect of booster doses of poliovirus vaccine in previously vaccinated children, clinical trial results 2013
Habib MA , Soofi S , Mach O , Samejo T , Alam D , Bhatti Z , Weldon WC , Oberste MS , Sutter R , Bhutta ZA . Vaccine 2016 34 (33) 3803-9 BACKGROUND: Considering the current polio situation Pakistan needs vaccine combinations to reach maximum population level immunity. The trial assessed whether inactivated poliovirus vaccine (IPV) can be used to rapidly boost immunity among children in Pakistan. METHODS: A five-arm randomized clinical trial was conducted among children (6-24months, 5-6years and 10-11years). Children were randomized in four intervention arms as per the vaccines they received (bOPV, IPV, bOPV+vitamin A, and bOPV+IPV) and a control arm which did not receive any vaccine. Baseline seroprevalence of poliovirus antibodies and serological immune response 28days after intervention were assessed. RESULTS: The baseline seroprevalence was high for all serotypes and the three age groups [PV1: 97%, 100%, 96%, PV2: 86%, 100%, 99%, PV3: 83%, 95%, 87% for the three age groups respectively]. There was significantly higher rate of immune response observed in the study arms which included IPV (95-99%) compared with bOPV only arms (11-43%), [p<0.001]; Vitamin A was not associated with improved immune response. Immune response rates in the IPV only arm and IPV+bOPV arm were similar [p>0.5]. CONCLUSION: IPV has shown the ability to efficiently close existing immunity gaps in a vulnerable population of children in rural Pakistan. |
Monovalent type-1 oral poliovirus vaccine given at short intervals in Pakistan: a randomised controlled, four-arm, open-label, non-inferiority trial
Mir F , Quadri F , Mach O , Ahmed I , Bhatti Z , Khan A , Rehman NU , Durry E , Salama M , Oberste SM , Weldon WC , Sutter RW , Zaidi AK . Lancet Infect Dis 2015 15 (8) 889-97 BACKGROUND: Supplementary immunisation activities with oral poliovirus vaccines (OPVs) are usually separated by 4 week intervals; however, shorter intervals have been used in security-compromised areas and for rapid outbreak responses. We assessed the immunogenicity of monovalent type-1 oral poliovirus vaccine (mOPV1) given at shorter than usual intervals in Karachi, Pakistan. METHODS: This was a multicentre, randomised, controlled, four-arm, open-label, non-inferiority trial done at five primary health-care centres in low-income communities in and around Karachi, Pakistan. Eligible participants were healthy newborn babies with a birthweight of at least 2.5 kg, for whom informed consent was provided by their parent or guardian, and lived less than 30 km from the study clinic. After receiving a birth dose of trivalent OPV, we enrolled and randomly assigned newborn babies (1:1:1:1) to receive two doses of mOPV1 with an interval of 1 week (mOPV1-1 week), 2 weeks (mOPV1-2 weeks), or 4 weeks (mOPV1-4 weeks) between doses, or two doses of bivalent OPV (bOPV) with an interval of 4 weeks between doses (bOPV-4 weeks). We gave the first study dose of OPV at age 6 weeks. We did the randomisation with a centrally generated, computerised allocation sequence with blocks of 16; participants' families and study physicians could not feasibly be masked to the allocations. Trial participants were excluded from local supplementary immunisation activities during the study period. The primary outcome was non-inferiority (within a 20% margin) between groups in seroconversion to type-1 poliovirus. The primary and safety analyses were done in the per-protocol population of infants who received all three doses of vaccine. This trial is registered with ClinicalTrials.gov, number NCT01586572, and is closed to new participants. FINDINGS: Between March 1, 2012, and May 31, 2013, we enrolled 1009 newborn babies, and randomly assigned 829 (82%) to treatment. 554 (67%) of the 829 babies were included in the per-protocol analysis. Proportions of seroconversion to type-1 poliovirus were 107/135 (79%, 95% CI 72.4-86.1) with mOPV1-1 week, 108/135 (80%, 73.2-86.8) with mOPV1-2 weeks, 129/148 (87%, 80.9-92.0) with mOPV1-4 weeks, and 107/136 (79%, 71.8-85.6) with bOPV-4 weeks. Non-inferiority was shown between groups and no significant differences were noted. Ten participants died during the trial. Seven of these deaths occurred during the lead-in period before randomisation (two from diarrhoea, five from unknown causes). Three infants died from sepsis after random assignment. No deaths were attributed to the procedures or vaccines. Additionally, we noted no events of vaccine-associated paralysis. INTERPRETATION: We identified no significant differences in responses to mOPV1 given with shorter intervals between doses than with the standard 4 week intervals. The short-interval strategy could be particularly beneficial when temporary windows of opportunity for safe access can be granted in areas of conflict-eg, during cease-fire periods. In such situations, we recommend shortening the interval between OPV doses to 7 days. FUNDING: World Health Organization. |
Severe human parechovirus type 3 myocarditis and encephalitis in an adolescent with hypogammaglobulinemia
Mardekian SK , Fortuna D , Nix A , Bhatti T , Wiley CA , Flanders A , Urtecho J , Sloane J , Ahmad J , Curtis MT . Int J Infect Dis 2015 36 6-8 Human parechovirus (HPeV) belongs to the Picornaviridae family of RNA viruses. HPeV infections can be asymptomatic, lead to mild respiratory and/or gastrointestinal symptoms, or less frequently cause severe diseases such as sepsis, meningitis, encephalitis, and myocarditis. Severe neurological HPeV infections occur most commonly in infants and neonates. There are currently 16 recognized types of HPeV. HPeV type 3 (HPeV3) has been the predominant type associated with severe central nervous system (CNS) disease in neonates and newborns since its discovery in 1999. Although HPeV-related infections have been reported in adults, symptomatic HPeV3 infections in adolescents and adults are uncommon. We describe a case of severe HPeV3 myocarditis and encephalitis in an adolescent. |
Immunogenicity of poliovirus vaccines in chronically malnourished infants: a randomized controlled trial in Pakistan
Saleem AF , Mach O , Quadri F , Khan A , Bhatti Z , Rehman NU , Zaidi S , Weldon WC , Oberste SM , Salama M , Sutter RW , Zaidi AK . Vaccine 2015 33 (24) 2757-63 Reaching high population immunity against polioviruses (PV) is essential to achieving global polio eradication. Efficacy of oral poliovirus vaccine (OPV) varies and is lower among children living in tropical areas with impoverished environments. Malnutrition found as a risk factor for lower serological protection against PV. We compared whether inactivated polio vaccine (IPV) can be used to rapidly close the immunity gap among chronically malnourished (stunted) infants in Pakistan who will not be eligible for the 14 week IPV dose in routine EPI schedule. A phase 3, multicenter 4-arm randomized controlled trial conducted at five Primary Health Care (PHC) centers in Karachi, Pakistan. Infants, 9-12 months were stratified by length for age Z score into chronically malnourished and normally nourished. Infants were randomized to receive one dose of either bivalent OPV (bOPV) alone or bOPV+IPV. Baseline seroprevalence of PV antibodies and serum immune response to study vaccine dose were assessed by neutralization assay. Vaccine PV shedding in stool was evaluated 7 days after a bOPV challenge dose. Sera and stool were analyzed from 852/928 (92%) enrolled children. At baseline, the seroprevalence was 85.6% (n=386), 73.6% (n=332), and 70.7% (n=319) in malnourished children against PV types 1, 2 and 3 respectively; and 94.1% (n=448), 87.0% (n=441) and 83.6% (n=397) in the normally nourished group (p<0.05). Children had previously received 9-10 doses of bOPV (80%) or tOPV (20%). One dose of IPV+bOPV given to malnourished children increased their serological protection (PV1, n=201, 97.6%; PV2, n=198, 96.1% and PV3, n=189, 91.7%) to parity with normally nourished children who had not received IPV (p=<0.001). Seroconversion and boosting for all three serotypes was significantly more frequent in children who received IPV+bOPV than in those with bOPV only (p<0.001) in both strata. Shedding of polioviruses in stool did not differ between study groups and ranged from 2.4% (n=5) to 7.1% (n=15). In malnourished children the shedding was reduced after bOPV+IPV compared to bOPV only. Chronically malnourished infants were more likely to be unprotected against polioviruses than normal infants. bOPV+IPV helped close the immunity gap better than bOPV alone. |
Zinc supplementation fails to increase the immunogenicity of oral poliovirus vaccine: a randomized controlled trial
Habib MA , Soofi S , Sheraz A , Bhatti ZS , Okayasu H , Zaidi SZ , Molodecky NA , Pallansch MA , Sutter RW , Bhutta ZA . Vaccine 2014 33 (6) 819-25 BACKGROUND: Polio eradication remains a challenge in Pakistan and the causes for the failure to eradicate poliomyelitis are complex. Undernutrition and micronutrient deficiencies, especially zinc deficiency, are major public health problems in Pakistan and could potentially affect the response to enteric vaccines, including oral poliovirus vaccine (OPV). OBJECTIVE: To assess the impact of zinc supplementation among infants on immune response to oral poliovirus vaccine (OPV). METHODS: A double-blind, randomized placebo-controlled trial was conducted in newborns (aged 0-14 days). Subjects were assigned to either receive 10mg of zinc or placebo supplementation daily for 18 weeks. Both groups received OPV doses at birth, at 6 weeks, 10 weeks and 14 weeks. Data was collected on prior immunization status, diarrheal episodes, breastfeeding practices and anthropometric measurements at recruitment and at 6 and 18 weeks. Blood samples were similarly collected to determine the antibody response to OPV and for micronutrient analysis. Logistic regression was used to determine the relationship between seroconversion and zinc status. RESULTS: Overall, 404 subjects were recruited. At recruitment, seropositivity was already high for poliovirus (PV) serotype 1 (zinc: 91.1%; control: 90.5%) and PV2 (90.0%; 92.7%), with lower estimates for PV3 (70.0%; 64.8%). By week 18, the proportion of subjects with measured zinc levels in the normal range (i.e. ≥60mug/dL) was significantly greater in the intervention group compared to the control group (71.9%; 27.4%; p<0.001). No significant difference in seroconversion was demonstrated between the groups for PV1, PV2, or PV3. CONCLUSIONS: There was no effect of zinc supplementation on OPV immunogenicity. These conclusions were confirmed when restricting the analysis to those with measured higher zinc levels. |
An international systematic review and meta-analysis of multisession psychosocial interventions compared with educational or minimal interventions on the HIV sex risk behaviors of people who use drugs
Meader N , Semaan S , Halton M , Bhatti H , Chan M , Llewellyn A , Des Jarlais DC . AIDS Behav 2013 17 (6) 1963-78 This systematic review and meta-analysis examines the effectiveness of multisession psychosocial interventions compared with educational interventions and minimal interventions in reducing sexual risk in people who use drugs (51 studies; 19,209 participants). We conducted comprehensive searches (MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials and PsychINFO 1998-2012). Outcomes (unprotected sex, condom use, or a composite outcome) were extracted by two authors and synthesised using meta-analysis. Subgroup analyses and meta-regression were conducted to explore heterogeneity. Multisession psychosocial interventions had modest additional benefits compared to educational interventions (K = 46; OR 0.86; 95% CI 0.77, 0.96), and large positive effects compared to minimal interventions (K = 7; OR 0.60; 95% CI 0.46, 0.78). Comparison with previous meta-analyses suggested limited progress in recent years in developing more effective interventions. Multisession psychosocial and educational interventions provided similar modest sexual risk reduction justifying offering educational interventions in settings with limited exposure to sexual risk reduction interventions, messages, and resources. |
Diagnostic X-ray examinations and increased chromosome translocations: evidence from three studies
Bhatti P , Yong LC , Doody MM , Preston DL , Kampa DM , Ramsey MJ , Ward EM , Edwards AA , Ron E , Tucker JD , Sigurdson AJ . Radiat Environ Biophys 2010 49 (4) 685-92 ![]() Controversy regarding potential health risks from increased use of medical diagnostic radiologic examinations has come to public attention. We evaluated whether chromosome damage, specifically translocations, which are a potentially intermediate biomarker for cancer risk, was increased after exposure to diagnostic X-rays, with particular interest in the ionizing radiation dose-response below the level of approximately 50 mGy. Chromosome translocation frequency data from three separately conducted occupational studies of ionizing radiation were pooled together. Studies 1 and 2 included 79 and 150 medical radiologic technologists, respectively, and study 3 included 83 airline pilots and 50 university faculty members (total = 155 women and 207 men; mean age = 62 years, range 34-90). Information on personal history of radiographic examinations was collected from a detailed questionnaire. We computed a cumulative red bone marrow (RBM) dose score based on the numbers and types of X-ray examinations reported with 1 unit approximating 1 mGy. Poisson regression analyses were adjusted for age and laboratory method. Mean RBM dose scores were 49, 42, and 11 for Studies 1-3, respectively (overall mean = 33.5, range 0-303). Translocation frequencies significantly increased with increasing dose score (P < 0.001). Restricting the analysis to the lowest dose scores of under 50 did not materially change these results. We conclude that chromosome damage is associated with low levels of radiation exposure from diagnostic X-ray examinations, including dose scores of approximately 50 and lower, suggesting the possibility of long-term adverse health effects. |
Predictors of 2,4-dichlorophenoxyacetic acid exposure among herbicide applicators
Bhatti P , Blair A , Bell EM , Rothman N , Lan Q , Barr DB , Needham LL , Portengen L , Figgs LW , Vermeulen R . J Expo Sci Environ Epidemiol 2010 20 (2) 160-8 To determine the major factors affecting the urinary levels of 2,4-dichlorophenoxyacetic acid (2,4-D) among county noxious weed applicators in Kansas, we used a regression technique that accounted for multiple days of exposure. We collected 136 12-h urine samples from 31 applicators during the course of two spraying seasons (April to August of 1994 and 1995). Using mixed-effects models, we constructed exposure models that related urinary 2,4-D measurements to weighted self-reported work activities from daily diaries collected over 5 to 7 days before the collection of the urine sample. Our primary weights were based on an earlier pharmacokinetic analysis of turf applicators; however, we examined a series of alternative weighting schemes to assess the impact of the specific weights and the number of days before urine sample collection that were considered. The derived models accounting for multiple days of exposure related to a single urine measurement seemed robust with regard to the exact weights, but less to the number of days considered; albeit the determinants from the primary model could be fitted with marginal losses of fit to the data from the other weighting schemes that considered a different numbers of days. In the primary model, the total time of all activities (spraying, mixing, other activities), spraying method, month of observation, application concentration, and wet gloves were significant determinants of urinary 2,4-D concentration and explained 16% of the between-worker variance and 23% of the within-worker variance of urinary 2,4-D levels. As a large proportion of the variance remained unexplained, further studies should be conducted to try to systematically assess other exposure determinants. |
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