Kidney360 Publish Ahead of Print, published on August 19, 2020 as doi:10.34067/KID.0003392020 Kidney Function, Self-Reported Symptoms, and Urine Findings in Nicaraguan Sugarcane Workers Zoe E. Petropoulos1, Rebecca L. Laws1, Juan José Amador2, Damaris López-Pilarte2, James S. Kaufman3,4, Daniel E. Weiner5, Oriana Ramirez-Rubio2,6, Daniel R. Brooks2, Michael D. McClean1, Madeleine K. Scammell1 1 Department of Environmental Health, Boston University School of Public Health, Boston, MA 2 Department of Epidemiology, Boston University School of Public Health, Boston, MA 3 Division of Nephrology, New York University School of Medicine, New York, NY 4 Division of Nephrology, VA New York Harbor Healthcare System, New York, NY 5 Division of Nephrology, Department of Medicine, Tufts Medical Center, Boston, MA 6 Non-Communicable Diseases and Environment Programme, Barcelona Institute for Global Health, Barcelona, Spain Corresponding Author: Zoe E. Petropoulos 715 Albany Street, Talbot 4 West Boston, MA 02118 617-358-2724 [email protected] Copyright 2020 by American Society of Nephrology. Abstract Background: An epidemic of chronic kidney disease in Central America predominantly affects males working in certain industries including sugarcane. Urinary tract infections are commonly diagnosed among men in Nicaragua, who often receive antibiotics and nonsteroidal anti-inflammatory drugs for urinary symptoms. Methods: We followed 251 male Nicaraguan sugarcane workers in seven job tasks over one harvest and measured urine dipstick parameters, kidney injury biomarkers, and estimated glomerular filtration rate (eGFR). We administered a questionnaire about urinary symptoms, health-related behaviors, and medication history. We cultured urine in a subset of workers. Results: The study population was composed of factory workers (22.7%), cane cutters (20.3%), irrigators (19.5%), drivers (16.3%), agrichemical applicators (11.6%), seeders/reseeders (6.0%), and seed cutters (3.6%). The mean age was 33.9 years and mean employment duration was 10.1 years. Cane cutters reported higher proportions of urinary-related symptoms compared with agrichemical applicators, irrigators, and seeders/reseeders. Seed cutters were more likely to take antibiotics (22.2%), while drivers and seeders/reseeders were more likely to take pain medications (26.8% and 26.7%, respectively). Proteinuria was uncommon, while dipstick leukocyte esterase was relatively common, especially among cane cutters, seed cutters, and seeders/reseeders (33.3%, 22.2%, and 21.4% at late-harvest, respectively). Dipstick leukocyte esterase at late-harvest was associated with a 12.9 mL/min/1.73m2 (95% CI: -18.7, -7.0) lower mean eGFR and 2.8 times (95% CI: 1.8, 4.3) higher mean neutrophil gelatinase-associated lipocalin (NGAL). In general, workers who reported urinary-related symptoms had higher mean kidney injury biomarker levels at late harvest. None of the workers had positive urine cultures, including those reporting urinary symptoms and/or with positive leukocyte esterase results. Amoxicillin, ibuprofen, and acetaminophen were the most commonly used medications. Conclusions: Job task is associated with urinary symptoms and dipstick leukocyte esterase. Urinary tract infection is misdiagnosed based on leukocyte esterase, which may be an important predictor of kidney outcomes. 2 Introduction An epidemic of chronic kidney disease (CKD) of uncertain etiology, often referred to as either CKDu or Mesoamerican nephropathy (MeN), has been affecting Central America for more than two decades. Traditional risk factors for CKD, such as hypertension and diabetes, are not implicated in CKDu in this region 1–5. This disease most often affects younger men employed in certain industries, including agriculture, mining, and brickmaking 2,3,6–8. Nicaragua has one of the highest CKD mortality rates in the world, particularly among younger men 9. Possible causes include known and potential nephrotoxins, such as heavy metals, agrichemicals, infectious agents, nonsteroidal anti-inflammatory drugs (NSAIDS), antibiotics, and other etiologies of intrinsic kidney injury such as sequelae of volume-related acute tubular necrosis. CKDu patients rarely exhibit high levels of proteinuria, but do appear to have elevated levels of tubular injury biomarkers, suggesting early tubulointerstitial damage 1–3,8,10–14, and kidney biopsies show interstitial fibrosis and tubular atrophy15–18. Hyperuricemia, dysuria, and sterile pyuria have also been reported in these populations 12,19,20. Interviews with physicians and pharmacists in two agricultural regions of Nicaragua indicate that patients frequently report symptoms consistent with urinary tract infections (UTIs) (e.g. dysuria, back pain) 21. In a sample of 61 Nicaraguan sugarcane workers, review of their medical records revealed that 69% received one or more UTI diagnoses, which were accompanied by urinalyses showing 75% had evidence of white blood cells, 35% had leukocyte casts, and 53% had crystalluria 22. A cross-sectional study among Costa Rican sugarcane workers found that harvesters were more likely than non-harvesters to experience dysuria once per week (28.3% vs 3.2%) 23 and a retrospective cohort study of Nicaraguan sugarcane workers reported that the odds of dysuria was 2.5-fold in cane cutters compared with other field jobs (95% CI 1.6-4.0) 24. These findings suggest a relationship between urinary symptoms and job task. Dysuria is so common in Nicaragua that a colloquial term, chistata, has emerged to describe a set of symptoms including painful urination, burning during urination, and back pain21. In El Salvador, the same common symptoms are referred to as mal de orina. Physicians in Nicaragua acknowledge that they frequently prescribe NSAIDs and antibiotics for patients with these symptoms, and many report diagnosing a UTI in men based on urine dipstick results alone 21, using urine cultures infrequently because of clinical protocols and 3 limited resources. Positive urine dipstick tests, which test for presence of leukocyte esterase and nitrites, may suggest infection, but are not specific. As UTIs are relatively uncommon in men compared to women, the routine diagnosis of UTIs in this predominantly male population at risk for CKDu is surprising and requires further investigation. The use of NSAIDs to treat dysuria may be a common practice throughout Central America, as indicated by a study in El Salvador that found that NSAID use (41.3%) and dysuria (39.1%) were common among a population largely working in agriculture 12. It has been hypothesized that the frequent use of nephrotoxic medications for these UTI-like symptoms may lead to or exacerbate kidney damage 25. It has also been suggested that kidney injury in these populations could be the result of chronic volume depletion due to occupational conditions, which could result in crystal-related symptoms due to high concentration of urinary urates 26,27. Diuretics are commonly prescribed to treat chistata 21, which could further increase volume depletion, thereby resulting in higher concentrations of urinary urates and other substances during the volume challenge experienced during heavy manual labor in excessive heat. Kidney damage could also result from the combination of these two pathways, along with other nephrotoxic exposures (e.g. agrichemicals, heavy metals). The objectives of this study, conducted among male Nicaraguan sugarcane workers, were to: (1) assess differences in self-reported symptoms and urine dipstick results across job categories, (2) determine the associations among self-reported symptoms, urine dipstick results, late-harvest kidney function, and kidney injury biomarkers, (3) describe patterns of medication use, and (4) determine whether workers with UTI-like symptoms and positive urine leukocyte esterase results have positive urine cultures. Methods Study Participants The study population and data collection methods have been described previously 13,28. Briefly, during October- December 2010 at the beginning of the harvest season (“pre-harvest”), sugarcane workers in Nicaragua were recruited and data were collected after a screening and hiring process conducted by the employer. Job applicants 4 with serum creatinine 1.4 mg/dl were not hired and therefore were not included in the study population. A second round of data collection≧ occurred near the end of the harvest season (“late-harvest”) during March-May 2011 among a subset of workers selected by convenience. Of the workers who participated in both rounds of data collection (n=506), a random sample (n=284) of workers was selected for analyses after excluding workers with more than one job and workers in certain job categories (e.g. maintenance workers, machine operators). This sample was primarily male (88.4%). The 33 women were not equally distributed amongst the job categories—2 factory workers, 10 seed cutters, and 21 seeders/reseeders—and did not include any cane cutters, the work category previously identified to be associated with the greatest risk of CKDu. Thus, the analyses in this study were restricted to men only (n=251) (see Supplemental Material for data on female participants). All participants were at least 18 years old. The final population represented workers from seven different job categories: drivers, factory workers, cane cutters, irrigators, agrichemical applicators, seed cutters, and seeders/re-seeders. Factory workers are employees of the sugarcane company who perform a variety of jobs, including operators, mechanics, and