Cystatin C could be a replacement to serum creatinine for diagnosing and monitoring kidney function in children.

BACKGROUND: Chronic kidney disease (CKD) is a worldwide public health problem. Glomerular filtration rate (GFR) is accepted as the best way to diagnose and monitor kidney function. Plasma Cystatin C (CysC) has been proposed as a better marker of GFR than serum creatinine (SCr), but it is not widely used because of some drawbacks with CysC assays. Our purpose is to determine the diagnostic accuracy of CysC and SCr for GFR estimation in children, using 99Tc-DTPA clearance (Cl(Tc)) as the reference standard. We also discuss some of the economic implications of these tests, in order to guide clinicians when to use CysC or SCr for the diagnosis or monitoring of CKD. METHODS: Data were collected from 109 Colombian outpatients aged less than 18 years referred for determination of GFR because of suspected or definite renal insufficiency. The cost of each test was determined in Bogotá, Colombia, and in Madrid, Spain. RESULTS: Using a GFR of 90 mL/min as a cut-off value, we found: CysC sensitivity 75%, specificity 84%, and area under ROC curve (AUC) 0.84. SCr sensitivity 46%, specificity 100%, and AUC 0.72. Using a GFR of 70 mL/min as a cut-off value, we found: CysC sensitivity 100%, specificity 48%, and AUC 0.94. SCr sensitivity 77%, specificity 91%, and AUC 0.81. In all calculations predictive values behave correspondingly and ranges were narrow at CI 95%. In AUC, p=0.0001. Cost per enzymatic test in Bogotá: CysC U$ 27; SCr U$ 2. Cost per enzymatic test in Madrid: CysC U$ 3; SCr U$ 0.08. CONCLUSION: CysC is a very interesting option, and could be a replacement to serum creatinine for diagnosing and possibly for monitoring kidney function in children.

Efecto del estrés ocasionado por las pruebas académicas sobre los niveles de cortisol y prolactina en un grupo de estudiantes de medicina / Effect of Stress Caused by Academic Tests on Cortisol and Prolactine Levels in a Group of Medical Students

Introducción: La relación entre el sistema inmune y el estrés ha sido motivo de debate en los últimos años. Los cambios neurohormonales generan variaciones en la respuesta inmunológica, con cambios importantes en los niveles de citoquinas lo que causa a su vez, en algunos casos, depresión de la respuesta citotóxica debida a la disminución de la población de células asesinas naturales (NK) (1). El estrés académico constituye un buen modelo para estudiar los cambios asociados en la secreción de algunas hormonas del eje Hipotalámico- Pituitario-Adrenocortical -HPA- (2, 3). Materiales y métodos: En el presente estudio se evaluó el comportamiento de las hormonas cortisol y prolactina, así como su incidencia en la respuesta adaptativa a Herpes Simple tipo I, en una población de estudio constituída por 26 estudiantes de la Facultad de Medicina, con edades comprendidas entre 14 y 27 años, con mayor frecuencia de género masculino (80.8%). Se realizó un estudio de intervención longitudinal en tres momentos, donde se midieron los niveles de cortisol, prolactina y anticuerpos contra Herpes Simple tipo I. Así mismo, se realizó una medición 15 días antes de la exposición al estresor, durante la aplicación del estresor (semana de exámenes trimestrales), y quince días después de la exposición al estresor. Todas las muestras fueron tomadas entre las 8:00 a.m. y las 10:00 a.m. Resultados y discusión: Se encontraron diferencias significativas (p < 0.001) en los valores promedio de prolactina, pues hubo una tendencia secular al aumento en los tres momentos evaluados. Para el cortisol, los cambios estuvieron cerca de mostrar diferencias significativas (p = 0.098), con un aumento en el momento del estresor y una disminución después del estresor. También hubo diferencias significativas (p = 0.043) en los niveles de anticuerpos para Her pes Simple tipo I, con una tendencia secular al aumento en los tres momentos evaluados. La respuesta adaptativa a Herpes Simple tipo I aumentó notoriamente como resultado de los cambios en la concentración de prolactina, la que, a su vez, aumentó de manera significativa después de la exposición al estresor. Aunque los niveles de cortisol no aumentan significativamente durante la semana del estresor, podrían ser suficientes para mantener niveles basales de prolactina, sin que haya un aumento de la respuesta adaptativa. Se podría inferir que el cortisol regula la síntesis de prolactina, pues en los resultados se observa que, a medida que disminuye la concentración de cortisol, los niveles de prolactina aumentan significativamente.

Introduction: The relationship between immunological system and stress has been debated in the last years. Neurohormonal changes produce immunologic response variations with major changes in the cytokines levels, causing depression of the cytolytic responses due to a decrease in the NK (Natural Killer) cells population (1). Academic stress is a useful stress model to study hormonal changes in the Hypotalamic-Pituitary- Adrenocortical (HPA) axis (2, 3). Materials and Methods: The present study evaluates the behavior of cortisol and prolactine hormones and their effect on the adaptative responses of Herpes Simplex Virus type I in a population of 26 medical students with ages between 14 and 27 years. Male students represented 80.8% of the evaluated population. This is a three stage longitudinal intervention study where antibodies, cortisol and prolactin levels were measured against Herpes Simplex Virus type I. The first measure was done 15 days previous to the stressful event, the second during the stressful event (mid-academic period exams) and the last one, 15 days posterior to the stressful event. All samples were taken from 8:00 am to 10:00 am. Results and Discussion: Prolactine average values were found to be significantly different (p < 0.001) when comparing the three stages. Cortisol values changes were near showing significant differences (p = 0.098), with an increase during the stressful event and a decrease after the exposure. Antibodies levels of Herpes Simplex Virus type I showed a significant difference (p = 0.043) increasing tendency in the three stages. Adaptative responses to Herpes Simplex Virus type I augmented as a result of prolactine concentration increase due to a stressor event exposure. This explains an increment in the cytotoxic cell activity (NK cells) which increment cytokine concentration, such as INF-α, which amplify humoral IgG antibody mediated response, according with obtained results. Even though cortisol levels do not significantly increased during the stressful event exposure, they could be enough to maintain basal prolactine levels without an adaptative response. It can be inferred that cortisol regulates the prolactine synthesis. Results show that when cortisol concentration decreases, prolactine levels significantly increase.