IDENTIFYING RISK FACTORS FOR CHRONIC KIDNEY DISEASE OF UNKNOWN ORIGIN IN SIX CENTRAL AMERICAN COUNTRIES AND HOUSTON, TEXAS

Chronic kidney disease (CKD) is a public health problem that is recognized worldwide. The type of CKD in Central America does not fit the “usual” CKD encountered in countries with upper middle-income economies, and is also often referred to as CKD of undetermined cause (CKDu). Evidence suggests that CKDu is a disease of occupational origin that can be brought on by a combination of exposures: hot environments, high physical job demands, inadequate hydration protocols, and effects of other nephrotoxic agents. Many gaps remain in knowledge related to CKDu and its putative risk factors, geographic distribution, distributions of renal function in certain demographics and countries as well as regarding feasibility of data collection and analytic methods. To address some of these gaps, I 1) estimated the prevalence and geographic distribution of potential CKDu risk factors among industry sectors in the six Spanish-speaking countries of Central America; 2) mapped the geographic variations of temperature patterns in relation to suspected CKDu risk factors and work-related CKD in the same countries; and 3) field tested the Disadvantaged Populations estimated Glomerular Filtration Rate (eGFR) Epidemiology (DEGREE) study protocol, outdoor point-of-care (POC) testing for serum creatinine, and a new risk factor module on CKDu for future use in U.S. outdoor Hispanic workers. A national representative survey titled The Second Central American Survey of Working Conditions and Health (II ECCTS by its Spanish acronym) was administered to a minimum of 1,500 workers per country, of both sexes, formal and informal workers, and in both urban and rural settings. The data from the II ECCTS were used to estimate the prevalence of CKDu risk factors and CKD risk. Overall descriptive statistics, prevalence of possible CKD and work-related CKD, and prevalence of CKDu risk factors and their distribution were calculated for the overall Central American region, and stratified by economic sector. Secondly, data collected from the II ECCTS were also used to better characterize the climate patterns and the geographic distribution of suspected CKDu risk factors in order to create a weather map to identify possible new “hot spots” in Central America. Finally, we conducted a pilot study of 50 Hispanic outdoor workers in Houston, where they completed the DEGREE and CKDu questionnaires, had anthropometrics and paired blood samples obtained for POC and laboratory assays of renal function at two different points in time (fall and spring). Findings from the national representative survey II ECCTS supplement the prior literature, demonstrating a high prevalence of self-attributed work-related CKD among 30 to 49-year-old mestizo males who worked in the primary and secondary sectors, and had physically demanding jobs. Geographically, most work-related CKD was concentrated in the central to western region of Central America associated with warm temperatures and also overlapped with persons reporting two or more CKDu risk factors. Moreover, there were several geographic areas of CKDu risk factors with no reported work-related CKDu, possibly reflecting as yet-undiscovered clusters of the disease. Implementation of the DEGREE and the new CKDu module was straightforward and well understood. The POC device performed well in the field, with some adjustment in methods when temperature readings were out of range. A combination of these methods can allow researchers to further explore CKDu and its risk factors both in new parts of Central America as well as in the U.S. among similar worker populations. This knowledge is needed so that preventive measures and interventions can be designed and implemented to prevent future cases of CKDu