Overweight, Obesity, Hypertriglyceridemia, and Insulin Resistance Are Positively Associated with High Serum Copper Levels in Mexican Adults.

Recently, the role of trace elements in the pathophysiology of obesity, insulin resistance (IR), and metabolic diseases has been explored. In this cross-sectional study, we aimed to assess the association of overweight, obesity, and cardiometabolic traits with serum copper (Cu) levels in 346 Mexican adults. Serum Cu level was measured by inductively coupled plasma mass spectrometry (ICP-MS). Anthropometrical data were collected, and biochemical parameters were measured. The triglyceride-glucose (TyG) index was used as a surrogate marker to evaluate IR. Overweight and obesity status was positively associated with the serum Cu level (ß = 19.434 ± 7.309, p = 0.008). Serum Cu level was observed to have a positive association with serum triglycerides level (ß = 0.160 ± 0.045, p < 0.001) and TyG (ß = 0.001 ± 0.001, p < 0.001). Additionally, high serum Cu level was positively associated with overweight and obesity status (odds ratio [OR] = 1.9, 95% confidence interval [95% CI] 1.1-3.4, p = 0.014), hypertriglyceridemia (OR = 3.0, 95% CI 1.7-5.3, p < 0.001), and IR (OR = 2.6, 95% CI 1.4-4.6, p = 0.001). In conclusion, our results suggest that overweight, obesity, hypertriglyceridemia, and IR are positively associated with serum Cu levels in Mexican adults.

Occupational Lead Exposure Ototoxicity Evaluated With Distortion-Product Otoacoustic Emissions.

OBJECTIVES: To evaluate the extent of hearing loss among pottery workers in Mexico exposed to lead. DESIGN: The authors conducted a cross-sectional study including 315 adult pottery workers. Auditory function was evaluated by air conduction pure-tone audiometry (pure-tone average) and distortion-product otoacoustic emission (DPOAE) levels (amplitude and signal-to-noise ratio). Lead exposure was assessed with a single blood sample test and classified as low, medium, and high according to blood lead tertiles. Logistic regression models were calculated for the association between blood lead levels, pure-tone average, and DPOAE records. RESULTS: Median (25th-75th) blood lead levels were 14 µg/dL (7.5-22.6 µg/dL). The audiometric pattern and DPOAE records were similar across blood lead levels groups in all frequencies, and no statistically significant differences were found. Adjusted logistic regression models showed no increase in the odds for hearing thresholds >25 dB (HL) and DPOAE absence associated with blood lead levels, and no dose-response pattern was observed ( p > 0.05). CONCLUSIONS: Given the results from this cross-sectional study, no association was found between blood lead levels and hearing loss assessed with DPOAE. Future longitudinal work should consider chronic lead exposure estimates among underrepresented populations, which can potentially inform safer work practices to minimize the risk of ototoxicity.

Assessment of miR-103a-3p in leukocytes-No diagnostic benefit in combination with the blood-based biomarkers mesothelin and calretinin for malignant pleural mesothelioma diagnosis.

Malignant pleural mesothelioma (MPM) is a cancer associated with asbestos exposure and its diagnosis is challenging due to the moderate sensitivities of the available methods. In this regard, miR-103a-3p was considered to increase the sensitivity of established biomarkers to detect MPM. Its behavior and diagnostic value in the Mexican population has not been previously evaluated. In 108 confirmed MPM cases and 218 controls, almost all formerly exposed to asbestos, we quantified miR-103-3a-3p levels in leukocytes using quantitative Real-Time PCR, together with mesothelin and calretinin measured in plasma by ELISA. Sensitivity and specificity of miR-103-3a-3p alone and in combination with mesothelin and calretinin were determined. Bivariate analysis was performed using Mann-Whitney U test and Spearman correlation. Non-conditional logistic regression models were used to calculate the area under curve (AUC), sensitivity, and specificity for the combination of biomarkers. Mesothelin and calretinin levels were higher among cases, remaining as well among males and participants ≤60 years old (only mesothelin). Significant differences for miR-103a-3p were observed between male cases and controls, whereas significant differences between cases and controls for mesothelin and calretinin were observed in men and women. At 95.5% specificity the individual sensitivity of miR-103a-3p was 4.4% in men, whereas the sensitivity of mesothelin and calretinin was 72.2% and 80.9%, respectively. Positive correlations for miR-103a-3p were observed with age, environmental asbestos exposure, years with diabetes mellitus, and glucose levels, while negative correlations were observed with years of occupational asbestos exposure, creatinine, erythrocytes, direct bilirubin, and leukocytes. The addition of miR-103a-3p to mesothelin and calretinin did not increase the diagnostic performance for MPM diagnosis. However, miR-103a-3p levels were correlated with several characteristics in the Mexican population.

Prestin and otolin-1 proteins in the hearing loss of adults chronically exposed to lead.

BACKGROUND: Some studies in animal models and humans suggest that exposure to lead is associated with hearing loss. Lead can reach the inner ear through the blood circulation; evidence suggests that lead could accumulate in the inner ear, causing inner ear damage. AIM: To evaluate prestin and otolin-1 protein levels and their relationship with an increased hearing threshold in participants exposed to lead. METHODS: We conducted a cross-sectional study with 315 participants from Tlaxcala, Mexico. Blood lead levels (BPb) were evaluated by graphite furnace atomic absorption spectrometry. Serum prestin and otolin-1 were quantified using ELISA. Auditory function at frequencies of 0.125 to 8 kHz was evaluated in a soundproof chamber. RESULTS: Participants were classified according to BPb: group I (<10 µg/dL) had a median BPb of 6 µg/dL and prestin levels of 11.06 ng/mL. While participants in group II (≥10 µg/dL) had a median of BPb 20.7 µg/dL (p < 0.05) and prestin levels of 0.15 ng/mL (p < 0.001). Participants in both groups showed a normal hearing. Otolin-1 levels were higher for participants with normal hearing and lower for participants with hearing loss in both groups, p > 0.05. Multiple linear regression models predict an average decrease of 0.17 to 0.26 ng/mL in prestin levels per decibel increase for the frequencies evaluated. CONCLUSIONS: Participants with high BPb showed an increase in hearing threshold, and prestin levels decreased proportionally to the hearing threshold increase. This is the first study to evaluate prestin as a potential biomarker for hearing damage, evaluated by audiometry, in participants with lead exposure.

Commute times and audiometric findings among adult population in Mexico City.

INTRODUCTION: Long commute times are common in big cities. OBJECTIVE: To determine hearing thresholds and their association with commute time in Mexico City. METHODS: Cross-sectional study that included 177 healthy adults from 2009 to 2011. Demographic information and commute times were recorded. Hearing was assessed by audiometry. Regression models were constructed to determine the predictors of hearing thresholds. RESULTS: There were 101 men (53%) and 76 women (43%). Mean commute time was 43 minutes (1-150 minutes). A hearing threshold drop was observed at 4000 Hz, with recovery at 8000 Hz in both ears when patients were stratified by gender and age groups. A commute time > 40 min/day increased the hearing threshold at 4000 Hz (ß = 2.96 dB HL, p < 0.01). Men had higher thresholds (ß = 2.6 dB HL), as older subjects also did: 25-34 years, ß = 2.2 dB HL; 35-44 years, ß = 5.2 dB HL; and ≥ 45 years, ß = 8.3 dB HL. CONCLUSION: The hearing pattern, although normal, resembled that of noise-induced hearing loss, associated with long commute times.

INTRODUCCIÓN: Los tiempos prolongados de traslado son comunes en las ciudades grandes. OBJETIVO: Determinar los umbrales auditivos y su asociación con el tiempo de traslado al trabajo en la Ciudad de México. MÉTODOS: Estudio transversal que incluyó a 177 adultos sanos de 2009 a 2011. Se registró información demográfica y tiempo de traslado al trabajo. La audición se evaluó mediante audiometría. Se realizaron modelos de regresión para determinar los predictores de los umbrales auditivos. RESULTADOS: Se trató de 101 hombres (53 %) y 76 mujeres (43 %). El tiempo promedio de traslado fue 43 minutos (1 a 150 minutos). Se observó una caída del umbral auditivo en 4000 Hz, con recuperación en 8000 Hz en ambos oídos al estratificar por sexo y grupos de edad. Un tiempo de traslado > 40 minutos/día incrementó el umbral auditivo en 4000 Hz (b = 2.96 dB HL, p < 0.01). Los hombres presentaron umbrales mayores (b = 2.6 dB HL), al igual que los sujetos de edad más avanzada: 25 a 34 años, b = 2.2 dB HL; 35 a 44 años, b = 5.2 dB HL y ≥ 45 años, b = 8.3 dB HL. CONCLUSIÓN: El patrón auditivo, aunque normal, se asemejó a la pérdida auditiva por ruido asociada a tiempo prolongado de traslado al trabajo.

Mesothelin, Calretinin, and Megakaryocyte Potentiating Factor as Biomarkers of Malignant Pleural Mesothelioma.

PURPOSE: Malignant pleural mesothelioma (MPM) is a highly lethal cancer caused by exposure to asbestos. Currently, the diagnosis is a challenge, carried out by means of invasive methods of limited sensitivity. This is a case-control study to evaluate the individual and combined performance of minimally invasive biomarkers for the diagnosis of MPM. METHOD: A study of 166 incident cases of MPM and 378 population controls of Mestizo-Mexican ethnicity was conducted. Mesothelin, calretinin, and megakaryocyte potentiating factor (MPF) were quantified in plasma by ELISA. The samples were collected from 2011 to 2016. RESULTS: Based on ROC analysis and a preset specificity of 95%, the combination of the three biomarkers reached an AUC of 0.944 and a sensitivity of 82% in men. In women, an AUC of 0.937 and a sensitivity of 87% were reached. In nonconditional logistic regression models, the adjusted ORs in men were 7.92 (95% CI 3.02-20.78) for mesothelin, 20.44 (95% CI 8.90-46.94) for calretinin, and 4.37 (95% CI 1.60-11.94) for MPF. The ORs for women were 28.89 (95% CI 7.32-113.99), 17.89 (95% CI 3.93-81.49), and 2.77 (95% CI 0.47-16.21), respectively. CONCLUSIONS: To our knowledge, this is the first study evaluating a combination of mesothelin, calretinin, and MPF, and demonstrating a sex effect for calretinin. The biomarker panel showed a good performance in a Mestizo-Mexican population, with high sensitivity and specificity for the diagnosis of MPM.

Determination of reference ranges for coagulation tests in Mexican-mestizo population / Determinación de límites de referencia de pruebas de coagulación en población mestizo-mexicana

Background: It is necessary to establish biological parameters for each population. Objective: To establish reference values for prothrombin time (PT), activated partial thromboplastin time (PTT) and fibrinogen in healthy population and to determine intra- and inter-assay concordance. Methods: Cross-sectional study that included 204 women and 202 men from the Blood Donor service. Coagulation tests were carried out in order to obtain reference ranges. All procedures were made according to the Clinical & Laboratory Standards Institute guidelines. Results: Mean PT, PTT and fibrinogen were 14.1 s, 28.8 s and 381 mg/dL in men, and 15.1 s, 29.0 s and 381 mg/dL in women. The proposed PT, PTT and fibrinogen reference ranges for men were 12.7 to 16.3 s, 24.2 to 36.3 s and 239 to 276 mg/dL, respectively; for women, 12.7 to 16.6 s, 23.5 to 35.4 s and 276 to 598 mg/dL. The latter was statistically significant (p ≤ 0.001). Conclusions: Reference values for blood coagulation tests were determined. This is of great importance for fast medical diagnosis and treatment. The results from this study can be adopted by other clinic laboratories after appropriate validation procedures.

Introducción: Es necesario establecer valores de referencia biológicos para cada población. Objetivo: Establecer los límites de referencia de tiempo de protrombina (TP), tiempo parcial de tromboplastina (TTP) y fibrinógeno en población mestizo-mexicana sana, así como la correlación y la concordancia en la determinación de estas pruebas con los dos equipos utilizados. Métodos: Estudio transversal en 204 mujeres y 202 hombres que acudieron al servicio de donadores y se les determinó TP, TTP y fibrinógeno para obtener los límites de referencia. Los procedimientos se realizaron de acuerdo con las guías del Instituto de Estándares de Laboratorio y Clínicos (CLSI C28-A3). Resultados: La media de TP, TTP y fibrinógeno en hombres fue de 14.1 s, 28.8 s y 381 mg/dL, y en mujeres de 15.1 s, 29.0 s y 381 mg/dL, respectivamente. Los límites de referencia para hombres en TP, TTP y fibrinógeno fueron de 12.7 a 16.3 s, de 24.2 a 36.3 s y de 239 a 276 mg/dL; para mujeres de 12.7 a 16.6 s, de 23.5 a 35.4 s y de 276 a 598 mg/dL, respectivamente. Este último fue estadísticamente significativo (p ≤ 0.001). Conclusiones: Se determinaron los límites de referencia para las pruebas de coagulación. Los resultados obtenidos en este estudio pueden ser adoptados por otros laboratorios clínicos, después de su apropiada validación.

Biomarkers for Predicting Malignant Pleural Mesothelioma in a Mexican Population.

Background: Diagnosis of malignant pleural mesothelioma (MPM) remains a challenge, especially when resources in pathology are limited. The study aimed to evaluate cost-effective tumor markers to predict the probability of MPM in plasma samples in order to accelerate the diagnostic workup of the tissue of potential cases. Methods: We conducted a case-control study stratified by gender, which included 75 incident cases with MPM from three Mexican hospitals and 240 controls frequency-matched by age and year of blood drawing. Plasma samples were obtained to determine mesothelin, calretinin, and thrombomodulin using enzyme-linked immunosorbent assays (ELISAs). We estimated the performance of the markers based on the area under the curve (AUC) and predicted the probability of an MPM diagnosis of a potential case based on the marker concentrations. Results: Mesothelin and calretinin, but not thrombomodulin were significant predictors of a diagnosis of MPM with AUCs of 0.90 (95% CI: 0.85-0.95), 0.88 (95% CI: 0.82-0.94), and 0.51 (95% CI: 0.41-0.61) in males, respectively. For MPM diagnosis in men we estimated a true positive rate of 0.79 and a false positive rate of 0.11 for mesothelin. The corresponding figures for calretinin were 0.81 and 0.18, and for both markers combined 0.84 and 0.11, respectively. Conclusions: We developed prediction models based on plasma concentrations of mesothelin and calretinin to estimate the probability of an MPM diagnosis. Both markers showed a good performance and could be used to accelerate the diagnostic workup of tissue samples in Mexico.

[Chronic kidney disease in Mexico and its relation with heavy metals]. / Enfermedad renal crónica en México y su relación con los metales pesados.

Chronic kidney disease (CKD) is a public health problem in Mexico, causing 25% of deaths related to diabetes mellitus (DM) and 28% related to hypertensive heart disease. In 2008 CKD reached the highest incidence of end-stage renal disease in the world. Diabetes mellitus is the main risk factor associated with CKD in Mexican population; however, heavy metals such as lead, arsenic, cadmium and mercury have been associated to nephropathies. In Mexico there are still high levels of these compounds in occupational and environmental settings; therefore, chronic exposures to these metals persist. In this review we approach to the main mechanisms of action of these metals in the body and its renal effects, as well as information about the sources of exposure to these chemical risks, the relationship between exposure to heavy metals and CKD, coupled with the economic and social consequences of this disease.

La enfermedad renal crónica (ERC) constituye un problema de salud pública en México, pues ocasiona el 25% de las muertes en pacientes con diabetes mellitus (DM) y 28% de las muertes relacionadas con cardiopatía hipertensiva. En 2008 la ERC alcanzó la tasa de incidencia más alta de enfermedad renal terminal en el mundo. La DM es el principal factor de riesgo asociado a la ERC en la población mexicana; sin embargo, los metales pesados como el plomo, el arsénico, el cadmio y el mercurio se han relacionado con las nefropatías. En México aún persisten niveles elevados de estos compuestos en diversos trabajos y en el ambiente, lo que condiciona una exposición crónica en la población. En esta revisión se describen los principales mecanismos de acción de estos metales en el organismo, así como sus efectos a nivel renal, además de información acerca de las fuentes de exposición a estos riesgos químicos, la relación entre la exposición a metales pesados y ERC, y, por último, las consecuencias económicas y sociales de esta enfermedad.

[Update on epidemiology, pathophysiology, diagnosis and treatment of malignant pleural mesothelioma]. / Actualización sobre la epidemiología, fisiopatología, diagnóstico y tratamiento del mesotelioma maligno pleural.

Malignant pleural mesothelioma is an occupational tumor caused by asbestos exposure. In Mexico, as asbestos usage is not prohibited, an increase in the number of cases is expected. Asbestos exposure is ubiquitous due to the great amount of products in which it is present. Its carcinogenicity is caused as the inhaled asbestos fibers cannot be eliminated by macrophages and, thus, they travel to the pleura through lymphatic pathways, producing a persistent inflammatory response. Diagnosis approach includes occupational history, along with clinical signs and symptoms, and paraclinical studies, such as pleural fluid cytology, chest x-rays, computed tomography, magnetic resonance imaging, and biopsy with immunohistochemistry. The main differential diagnosis is lung adenocarcinoma. Regarding the treatment of this tumor, it mainly comprises palliative care, even though chemotherapy, radiotherapy, and, in selected cases, surgical treatments have been used. There is an urgent need for general physicians and specialists to identify asbestos exposure, in order to make a timely diagnosis. Research is necessary to develop screening and prompt diagnostic tools, along with an epidemiological surveillance program for the workers and the general population exposed to asbestos.

El mesotelioma maligno pleural es un tumor ocupacional ocasionado por la exposición a cualquier tipo de fibra de asbesto. Y dado que en México el uso del asbesto no está prohibido, se espera que la incidencia de este tumor siga aumentando. La exposición al asbesto es ubicua, debido a la gran diversidad de productos en los que se encuentra. Su carcinogenicidad está dada porque las fibras de asbesto inhaladas no pueden ser eliminadas por los macrófagos y viajan hacia la pleura por vía linfática, donde producen una reacción inflamatoria persistente. Para su diagnóstico se precisa de una historia clínica laboral, además de que hay que orientarse con base en el cuadro clínico y los estudios paraclínicos, como la citología de líquido pleural, radiografía de tórax, tomografía axial computarizada, resonancia magnética y biopsia con inmunohistoquímica. El principal diagnóstico diferencial es el adenocarcinoma de pulmón. El tratamiento es principalmente paliativo, aunque se ha utilizado quimioterapia, radioterapia y, en seleccionados casos, cirugía. Para lograr un diagnóstico oportuno y certero es de vital importancia identificar las exposiciones al asbesto. Por otra parte, es necesaria la investigación para desarrollar pruebas de diagnóstico temprano y tamizaje, además de un programa de vigilancia epidemiológica para los trabajadores y la población general expuesta al asbesto.

Increased Cardiovascular Risk Using Atherogenic Index Measurement Among Healthcare Workers.

BACKGROUND AND AIMS: Cardiovascular diseases are one of the leading causes of death worldwide. This burden of disease is particularly high among healthcare workers. The aim of the study was to identify determinants that increase atherogenic index among healthcare workers. METHODS: In 1,678 healthcare workers, cardiovascular risk factors were analyzed: body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, glucose, total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides. Atherogenic index was calculated and determinants were identified. RESULTS: Mean (SD) age was 41.2 (8.4) years; body mass index 28.4 (4.8); waist-hip-ratio 0.88 (0.07); glucose 96.6 (22.2) µg/dL; TC 195.3 (50.3) mg/dL; HDL 49.0 (16.3) mg/dL; LDL 112.7 (35.0) mg/dL; triglycerides 171.7 (121.2) mg/dL; and atherogenic index 3.3 (1.5). Overweight and obesity prevalence was 77.2%. In the multiple linear regression model, the coefficients for AI were being a physician ß = 0.381, male gender = 0.443, BMI ß = 0.35, waist-to-hip ratio ß = 2.15, age = 0.014, and triglycerides ß = 0.915. CONCLUSIONS: The main contributors to atherogenic index increase were male sex, increased age, waist-to-hip ratio increase, overweight and obesity, high triglyceride levels and working as a physician. Although waist-to-hip ratio was the most powerful determinant, the physician occupational category added risk factors such as stress and adverse psychosocial working conditions, which may potentiate cardiovascular diseases.

Malignant Pleural Mesothelioma: Accuracy of CT Against Immunohistochemical Test Among the Mexican Population.

BACKGROUND AND AIMS: Malignant pleural mesothelioma (MPM) is associated with occupational and environmental exposure to asbestos. The incidence is expected to increase as the use of asbestos is not prohibited in many countries, such as in Mexico. We undertook this study to determine sensitivity, specificity, predictive values and likelihood ratios of computed tomography (CT) in a sample from Mexican population with suspected MPM and other pleuropulmonary diseases. METHODS: CT films of 38 patients suspected of having MPM were analyzed. A single observer was blinded to MPM diagnoses. The frequencies of ten CT findings were identified. A cut-off point of ≥5 CT findings was established to determine high MPM probability. Sensitivity, specificity, predictive values and likelihood ratio of the CT against biopsy using immunohistochemical testing (IHC) for MPM were calculated. RESULTS: Of the 38 patients, 31 had MPM and seven had lung adenocarcinoma. The five key findings were mediastinal pleural thickening 96.7% (n = 30), nodular pleural thickening 93.3% (n = 29), pleural mass 83.9% (n = 26), diminished lung 70.9% (n = 22) and contracted hemithorax 70.9% (n = 22). Sensitivity 96.8% (83.2-99.4), specificity 85.7% (42.2-97.6), positive likelihood ratio 6.7 (1.1-41.6), and negative likelihood ratio of 0.04 (0.01-0.2) were reported. CONCLUSIONS: Sensitivity and specificity in this study was greater than previously reported, 96.8% and 85.7 vs. 93.2 and 65.6%, respectively. CT is an easily accessible and useful tool that should be incorporated into the medical education of general physicians to improve MPM diagnosis of suspected cases.

[Concordance in blood lead quantification between laboratories]. / Concordancia interlaboratorios en la cuantificación de plomo en la sangre.

OBJECTIVE: To establish a blood lead quantification correlation from two occupational health laboratories (OHL1V and OHL2DF), and the ABC Hospital (LABC) metals laboratory. METHODS: A cross-sectional study was performed in 84 workers from a voltage regulators company, where lead is welded; in 54 % (46 of them) a blood sample was taken and analyzed by OHL1V, and in 28.6 % (24) by OHL2DF. All samples were analyzed by atomic absorption spectrophotometry. Pearson correlation (r), coefficient of determination (r2), Lin (rho) concordance test, and Bland-Altman plots were calculated. RESULTS: The blood lead mean: LABC was 5.8 ± 2.4 µg/dL vs. OHL2DF of 4.4 ± 3.6 µg/dL (r = 0.25 [p = 0.24], r2 = 0.06 [p = 0.24], and rho = 0.21 [p = 0.21]). And with LABC, 6.75 ± 3.3 µg/dL vs. OHL1V 5.6 ± 2.9 µg/dL (r = 0.91 [p < 0.001], r2 = 0.83 [p < 0001], and rho = 0.85 [p< 0.001]). CONCLUSIONS: Agreement between LABC and OHL1V was poor (< 0.90), and with OHL2DF was null. An occupational health laboratory certification is needed in order to have reliable biological exposure index measurements in lead occupational exposure.

OBJETIVO: determinar la concordancia de las cuantificaciones del plomo en la sangre de dos laboratorios del Instituto Mexicano del Seguro Social (LST1V y LST2DF), con las del Laboratorio de Metales del Hospital ABC (LABC). MÉTODOS: se realizó un estudio transversal en 84 trabajadores que sueldan con plomo en una empresa de reguladores. Se tomaron muestras de sangre; 100 % fue analizado por el LABC, 54 % (46) por el LST1V y 28.6 % (24) por el LST2DF. Todas las muestras se analizaron por espectrofotometría de absorción atómica. Se calculó la correlación de Pearson (r), el coeficiente de determinación (r2), la concondancia de Lino (rho) y las gráficas de Bland-Altman. RESULTADOS: las muestras analizadas en el LST2DF indicaron 4.4 ± 3.6 µg/dL de plomo en la sangre y en el LABC, 5.8 ± 2.4 µg/dL (r = 0.25 [p = 0.24], r2 = 0.06 [p = 0.24] y rho = 0.21 [p = 0.21]). Las muestras analizadas en el LST1V indicaron 5.6 ± 2.9 µg/dL y en el LABC, 6.75 ± 3.3 µg/dL (r = 0.91 [p< 0.001], r2 = 0.83 [p< 0.001] y rho = 0.85 [p< 0.001]). CONCLUSIONES: los resultados del LABC concordaron pobremente con los del LST1V (< 0.90) y no lo hicieron con los del LST1-DF. Es necesario certificar a los laboratorios institucionales y acreditar a los técnicos que realizan los análisis, para obtener resultados confiables de los indicadores biológicos de exposición ocupacional.