Antonio Urda-Cardona

Epidemiología de los ingresos por bronquiolitis en el sur de Europa: análisis de las epidemias 2010-2015

espanolIntroduccion La renovacion de las guias de practica clinica sobre la bronquiolitis aguda (BA) obliga a reevaluar las consecuencias de su implantacion. Pretendemos actualizar las principales variables clinico-epidemiologicas en pacientes ingresados por BA en el sur de Europa y analizar las causas de la estancia prolongada. Pacientes y metodo Estudio retrospectivo de ingresos por BA durante 5 epidemias (2010-2015), con descripcion de las principales variables clinico-epidemiologicas y analisis por regresion logistica de los factores asociados a mayor estancia. Resultados El inicio de la epidemia ocurrio entre las semanas cuarta de septiembre y tercera de octubre. De los menores de 2 anos (42.530 ninos), el 15,21% (6.468 pacientes) acudieron a urgencias por BA y el 2,36% ingresaron (1.006 pacientes), con un 18,5% de prematuros. El 12,2% tenian peso al nacimiento inferior a 2.300g. El 21,1% eran menores de un mes, consultaron por apnea asociada el 10,8%, ingesta inferior al 50% en el 31,1% y presentaban sobreinfeccion bacteriana el 13,1%. Estos factores se asociaron de forma independiente a la estancia prolongada. La mediana de estancia fue de 5 dias y la proporcion de ingresos en la unidad de cuidados intensivos pediatricos (UCIP) del 8,5% de los casos. Conclusiones El inicio de la epidemia de la bronquiolitis mostro una variabilidad de hasta 4 semanas en nuestro medio. Tras 5 anos de la implantacion de la guia de practica clinica, la incidencia de ingresos esta en torno al 2,3% y parece estable respecto a estudios previos. La edad media de los pacientes desciende a 2,4 meses, aunque con una proporcion similar de ingresos en la UCIP de un 8,5%. Los factores de riesgo independiente asociados a una estancia hospitalaria mas prolongada fueron: bajo peso al nacimiento, edad menor de un mes, apneas previas al ingreso, ingesta inferior al 50% y la sobreinfeccion bacteriana grave, donde la infeccion respiratoria supero la prevalencia de infeccion del tracto urinario grave. EnglishIntroduction The renewal of clinical practice guidelines on acute bronchiolitis (AB) requires the re-assessment of the consequences of their implementation. An update is presented on the main clinical and epidemiological variables in patients hospitalised due to AB in Southern Europe and an analysis made of the causes associated with longer hospital stay. Patients and method A retrospective study was conducted on patients admitted to hospital due to AB during 5 epidemics (2010-2015), with an analysis of the major clinical and epidemiological variables. A logistic regression analysis was performed on the factors associated with a longer hospital stay. Results The beginning of the epidemic occurred between the 4th week of September and the 3rd week of October. Of those children under 2 years (42,530), 15.21% (6,468 patients) attended paediatric emergency department due to having AB, and 2.36% (1,006 patients) were admitted. Of these, 18.5% of were premature, 12.2% had a birth weight Conclusions The beginning of the bronchiolitis epidemic showed a variability of up to 4 weeks in this region. Five years after implementing the new guidelines, the incidence of admissions was approximately 2.3%, and appeared stable compared to previous studies. The mean age of the patients decreased to 2.4 months, although with a similar proportion of PICU admissions of 8.5%. Independent factors associated with prolonged stay were: low birth weight, age less than one month, apnoea prior-to-admission, intake of less than 50%, and severe bacterial superinfection. Respiratory bacterial infection exceeded the prevalence of urinary tract infection.INTRODUCTION The renewal of clinical practice guidelines on acute bronchiolitis (AB) requires the re-assessment of the consequences of their implementation. An update is presented on the main clinical and epidemiological variables in patients hospitalised due to AB in Southern Europe and an analysis made of the causes associated with longer hospital stay. PATIENTS AND METHOD A retrospective study was conducted on patients admitted to hospital due to AB during 5 epidemics (2010-2015), with an analysis of the major clinical and epidemiological variables. A logistic regression analysis was performed on the factors associated with a longer hospital stay. RESULTS The beginning of the epidemic occurred between the 4th week of September and the 3rd week of October. Of those children under 2 years (42,530), 15.21% (6,468 patients) attended paediatric emergency department due to having AB, and 2.36% (1,006 patients) were admitted. Of these, 18.5% of were premature, 12.2% had a birth weight <2,300g, 21.1% were younger than 1 month, 10.8% consulted for associated apnoea, 31.1% had an intake <50%, and 13.1% had bacterial superinfection. These factors were independently associated with prolonged stay. The median length of stay was 5 days, and 8.5% of cases were admitted to a paediatric intensive care unit (PICU). CONCLUSIONS The beginning of the bronchiolitis epidemic showed a variability of up to 4 weeks in this region. Five years after implementing the new guidelines, the incidence of admissions was approximately 2.3%, and appeared stable compared to previous studies. The mean age of the patients decreased to 2.4 months, although with a similar proportion of PICU admissions of 8.5%. Independent factors associated with prolonged stay were: low birth weight, age less than one month, apnoea prior-to-admission, intake of less than 50%, and severe bacterial superinfection. Respiratory bacterial infection exceeded the prevalence of urinary tract infection.

OC-38 Plasma arginine and hypertension in paediatricpatients with overweight

Introduction obesity (OB) is one of the most serious public health problems of the 21 st century, especially associated with complications, among which the predisposition to hypertension. There are conflicting data on the relationship between arginine levels and the presence of hypertension in adults, with almost no data on children. Material and methods A prospective longitudinal observational study of cohorts. Case = high weight (overweight (BMI>p85) and obese (OB) (BMI>p95)); control = normal weight (BMI p95 respectively Children 6–11 years old, prepubertal (Tanner 1–2) were selected. Exclusion criteria: secondary obesity, other organic disease, chronic intake of drugs or diabetes. Plasma arginine levels were measured by tandem mass spectrometry (mmol/L) at initial recruitment and after 12–15 months. One year follow-up of patients repeating clinical measurements of blood pressure, anthropometry and analytical data (arginine). Results 100 children, 52% male, with a mean age of 8.6±1.6 years; 71% overweight and overweight (63% obese); 79 children with waist circumference above p90. Arginine has no correlation with any of the analytical parameters or with the percentiles of BP and there is no statistically significant difference between baseline arginine levels according to the presence of insulin resistance, overweight or obesity Patients with high blood pressure at initial moment and after one year follow up have lower levels of plasma arginine (p<0.05). Among patients with a valid measure of BP after one year, 55% have a baseline arginine less than 20 mmol/L and, among them, 59% presented a rise in blood pressure above the 90th percentile (p 0.006), with an odds ratio of 7.22 (1.60–32.46), p 0.006. Discussion Our work provides evidence that there is an already valuable arginine deficit a few months before a tensional increase above the 90th percentile. Biochemical data are provided that can serve as predictors at an age where there may be reversibility of the ”hypertensive gait” process. These findings may elucidate new pathogenic mechanisms in adult hypertension begins in childhood, especially in the case of overweight patients.

P233 Enteral nutrition in children with life-threatening or life-limiting diseases in a paediatric palliative care/home hospitalisation unit

Introduction Nutritional support in the care of children with threatening or limiting diseases is based on improving their nutritional status and quality of life. Malnutrition is common in these patients due to swallowing disorders, maldigestion or malabsorption, and to chronic diseases with increased energy expenditure, losses or requirements. Methods A descriptive, retrospective analysis of patients with life-threatening or life-limiting diseases receiving Enteral Nutrition (EN) from 2000 to 2016, admitted to a Paediatric Palliative Care/Home Hospitalisation Unit, has been performed. Results 188 patients have been treated. The mean age was 2.8 years (IR: 24 days-15.8 years). The most frequent indications were: swallowing disorders (42%), malnutrition (13.8%) and failure to thrive (12.2%). According to the classification of the Association for children with life threatening situation or terminal situation and their families: • Group 1 (Diseases for which curative treatment may be feasible but may fail): 23.9% (heart disease 75.5%, cancer 17.8%) • Group 2 (Diseases for which premature death is anticipated, but intensive treatment may prolong good-quality life and participation in normal childhood activities): 26.6% (Gastrointestinal (GI) diseases and malformations 48%) • Group 3 (progressive diseases for which treatment is exclusively palliative): 21.3% (57.5% advanced or metastatic cancer, 20% neuromuscular diseases) • Group 4 (severe, non-progressive neurological impairment resulting in vulnerability and complications that may lead to premature death): 28.2% (39.6% hypoxic encephalopathy) Enteral feeding was performed through a nasogastric tube in most patients (83%), requiring gastrostomy in 23.4%. During this time period, 49 patients (26%) died in relation to their underlying disease except for one due to surgical complication of the gastrostomy. Conclusions Neurological and oncological patients represent the most frequent pathologies requiring EN. In our study, children with congenital heart disease represent the third pathology in frequency, above GI diseases. Nutrition, along with symptom control, is one of the most important aspects of treating patients with limiting or life-threatening situations, half of which will require specialised palliative care.

OC-72 Faecal calprotectin in preterm newborn and its elevation in severe illness

Introduction Faecal calprotectin (FC) has been proposed as an inflamatory marker both in children and adults, with high levels registered in full-term newborn and in preterm newborn (PTNB). Nevertheless, there is scarce data about kinetics in the first month and its relation with severe illness such as systemic infections or bowel injury. Aims To determine normal levels of FC in PTNB and relate it with feeding-type, gestational age (GA), birth-weight and delivery method. Also checking if its figures increase days before the occurrence of symptoms in bowel inflamatory alterations and systemic infections. Materials and methods Observational clinic-analytic longitudinal prospective study through randomised selection of PTNB≤35 weeks GA, from whom faecal samples were taken in days 4, 8, 15, 30, 60 and 90 of life to determine FC (µg/g of faeces, CALPREST® from Eurospital). As significant illness we considered clinical or analytical sepsis or bowel injury/stress. All the variables of interest in the patient’s clinical history were collected. Breast-feeding was considered predominant if>80% of the feeding was reached through this method. Results 369 samples were taken from 114 PTNB. Mean GA was 30.2 (±2.38) weeks, with mean weight of 1376.9 (±429.16) grams. 72 children did not suffer any clinical event, giving a total of 76 patological events in 42 newborns (36.8% from the PTNB). No statistically significant differences were found in PTNB between beeing breast-fed or with formula, nor was difference found in those of different GA, except for those with birth-weight≥1500 g or<1500 g at day 8 of life (respectively 321.05±193.01 vs 169.67±134.22). Mean FC in healthy PTNB is significantly lower than in those who suffer illness, being statistically significant between days 4 and 30, days 4 and 15 and days 8 and 15. ConclutionS A high mean of calprotectin was observed in all cases ( higher in the first 4 days, statiscally significant, slight posterior decrease and stabilisation through the first months). During intercurrent diseases (systemic infections and intestinal distress), CF increases before the onset of symptoms or elevation of acute phase reactants and it remains 8–10 days elevated after the improvement. It is possible to use it as a predictor of digestive pathology in PTRB.

OC-39 Cardiac involvement in inherited metabolic diseases

Background and aims Inherited metabolic diseases (IMD) have an increasing prevalence, and can be detected by neonatal screening, at their onset as an acute decompensation or a chronic disease. The heart is a target organ in these disorders and can compromise the patient life if no early treatment is employed. The aim of this study is to describe the cases occurred in a tertiary children hospital and to analyse the heart involvement. Methods Retrospective study of 14 cases diagnosed with cardiomyopathy associated to IMD in a tertiary children’s hospital from January 2010 to January 2017. Results among the 14 cases described, 4 were lysosomal storage disorders (2 Pompe diseases, 1 Hunter disease (HD), 1 mucopolysaccharidosis type IX (Sly syndrome), 7 β-oxidation disorders (3 CPT2 deficiency, 2 carnitine transporter deficiency, 2 VLCAD), 1 glycosylation defect, 1 atypical progeroid syndrome (APS) and 1 glycine encephalopathy. Regarding cardiac involvement, hypertrophic cardiomyopathy was the most frequent one (8 cases), followed by rhythm disorders (1 VLCAD deficiency with paroxysmal supraventricular tachycardia, 3 CPT II deficiency with lethal neonatal form), 1 case of dilated cardiomyopathy and 1 severe pulmonary hypertension with secondary cardiac failure. 11 cases were diagnosed at disease onset and only in 3 cases the cardiac involvement emerged during the course of the disease, having been previously diagnosed with the underlying disease (HD, VLCADD, APS). 6 patients died and 4 developed sequelae from the underlying diseases or the heart involvement. Only 4 remain healthy, with remission of the cardiomyopathy. Treatment was pharmacological for all patients except for the HD one, who required surgery because of broken mitral valve, and the APS who needed a heart transplantation because of severe dilated cardiomyopathy. Symptomatic treatment in all patients with 3 patients under enzymatic replacement treatment (HD and Pompe). Conclusions cardiomyopathy is commonly associated with IMD, with the hyperthophic cardiomyopathy as the most frecuent one. Other heart involvement can be found (arrhythmia, progressive heart failure o postransplant complications), because of the evolution of the underlying disease or clínical deteroration after acute decompensations. We would like to highlight that neonatal screening facilitates an early diagnosis of some of these diseases (4 cases in our series) and can be the diagnostic key before or after cardiomyopathy manifestation, helping with therapeutic management or genetic counselling, taking into account that these entities have a high mortality (46% in our series).

OC-64 Hemopahagocytic lymphohistiocytosis: is it really important to make a difference between primary and secondary cases?

Background and aims Despite HLH-04 diagnostic criteria and treatment protocol for hemophagocytic lymphohistiocytosis (HLH) were proposed for both primary (pHLH) and secondary (sHLH) cases, several experts have criticised they are not optimum for the latter. The aims of this investigation are to describe the features of HLH patients that can help to differenciate between primary and secondary cases. Methods Retrospective descriptive study in of HLH patients from 0 to 14 years, diagnosed according to HLH-04 criteria, in a tertiary Paediatric Hospital during the last 10 years (Jan2007-Jan2017). Clinical, analytical and therapeutic data were retrospectively collected from medical records. pHLH and sHLH features were compared in a bivariant analysis. Statistical significance was considered as p<0.1. Results We found 13 patients, 3pHLH and 10sHLH, whose features are described in Table 1. The median age was 1.5 years (IR: 0.75–3.3), earlier in primary cases (1.0y vs 1.8y), though not significantly. 2 of 3 pHLH had grey hair and neurological impairment and were part of a consanguineous Moroccan family, with cousins diagnosed with Griscelli syndrome, so pHLH was suspected since the begining. CNS injury was more frequent in pHLH (66%) than in sHLH (10%)(p=0.04). There were no significant differences between other organ involvement. At onset, ferritin (p=0.043), neutrophils (p=0.05) and platelets (p=0.28) values were higher in sHLH than in pHLH. Lowest number of neutrophils (p=0.028), highest LDH levels (p=0.036) and minimum platelets count (p=0.07) were higher in sHLH too. There were no differences in other analytical features. Regarding treatment, pHLH cases needed steroids more often (p=0.06), as well as agressive therapies as etoposide (p=0.05) and intrathecal methotrexate (p=0.05). Mortality was significantly higher in primary group (p=0.03). ConclutionS In our experience pHLH and sHLH have important disparities according to evolution, mortality and treatment. Although 2 of our pHLH had physical appereance and family background that helped with etiological diagnosis, it is not always that easy. In this study, we found pHLH and sHLH have important differences, according to clinical and laboratory findings, that may have implications in subsequent management. Larger multicentric More studies are required to establish specific diagnostic criteria and therapeutic schemes depending on the aetiology. Abstract OC64 Table 1 Features of primary and secondary HLH in a tertiary Paediatric Hospital pHLH (n=3) sHLH (n=10) pHLH (n=3) sHLH (n=10) Male, n (%) 2 (66.7) 3 (30) Age (years), median (IR) 1 (0.5–1) 1.8 (0.8–4) Aetiology, n (%) Griscelli syndrome: 2 (66.7) Viral infections:6 (60): 3 CMV, 2 EBV, 1 MUNC deficiency: 1 (33.3) Enterovirus Rheumatic diseases:2 (20) Length of fever at diagnosis (days), median (IR) 7 (2–7) 8 (2.7–11.7) Organ involvement  Liver 2 (66.7) 1 (10)  CNS 2 (66.7) 1 (10)  Kidney 0 (0) 1 (10)  Hemodinamics 0 (0) 3 (30)  Lung 0 (0) 1 (10) Hepatomegaly, n (%) 3 (100) 10 (100) Splenomegaly, n (%) 3 (100) 9 (90) Haemoglobin (mg/dl), median (IR)  aD 7.6 (6.9–7.6) 9 (8.4–9.9)  Lv 6.5 (5.6–6.7) 7.6 (6.5–8.7) Neutrophils/mm3, median (IR)  aD 560 (400-600) 2050 (775–6450)  Lv 300 (20-300) 941 (547–1480) Ferritin (µg/L), median (IR)  aD 1651 (1392–1720) 7222 (3140–14922)  Hv 2187 (564–2324) 7222 (3735–14636) Fibrinogen (mg/dL), median (IR)  aD 167.7 (84–172) 157.5 (92.2–344.5)  Lv 56.7 (28.9–61.2) 91.5 (51.9–91.5) ALT (U/l), median (IR)  aD 102 (78-105) 176.5 (121–300)  Hv 133 (105-142) 383.5 (135–529) Hemophagocytosis in bone marrow n (%) 2 (66.7) 2 (33.3)*1 Treatment, n (%)  Steroids 3 (100) 4 (40)  Cyclosporine A 1 (33.3) 2 (20)  Etoposide 2 (66.7) 0 (0)  Intrathecal methotrexate 1 (33.3) 0 (0)  Plasmapheresis/IVIG 1 (33.3) 3 (30)  Underlying disease therapy 1 (33.3) 7 (70) Deaths, n (%) 3 (100) 1 (10) *1: Bone marrow biopsy in only 6 patients. aD: At diagnosis; Lv: Lowest value; Hv: Highest value; IVIG: Intravenous immunoglobulins

OC-33 Eosinophilic esophagitis, an emerging paediatricdisease

Background and aimS Eosinophilic esophagitis (EoE) is an ever growing clinical-pathological condition that generates great morbility and in which symptom control still presents itself as a challenge, having a variety of therapies described throughout the medical literature. The aim of this study is to review the cases handled by our unit in a 6 year period. Methods Retrospective descriptive unicentric study which analyses clinic, diagnostic methods, indirect disease markers, allergy tests and therapy employed in patients diagnosed with EoE between january 2008 and december 2014. Diagnosis was established with>15 eosinophils (Eos) per high power field (HPF) in esophageal epitelium associated to unresponsiveness to exclusive antiacid treatment. Results Data from 29 patients was collected, 75.9% male. Mean clinical debut age was 9.1±3.6 years, with a 0.4 years-delay to diagnostic (IQR 0.2–1) and follow-up time of 3 years (IQR 1.9–4). History of allergies was present in 31%. Sensitisation to food allergens was found in 44.7% of the patients, whilst 27.6% were sensitised to pneumoallergens. Various histological alterations were found, 2 of them with pronounced collagenation of the lamina propria in the whole length of the oesophagus, and 1 which presented simultaneous waves and incomplete relaxation of the lower esophageal sphincter in the manometry. Concerning treatment, 13.8% were on exclusion diet, 3.8% used elemental formulas and 37.9% carried out both simultaneously. Montelukast was employed in 27.6%, proton pump inhibitors in 41.4%, viscous oral budesonide (VOB) in 31%, swallowed fluticasone in 3,4%, whilst systemic steroids were used in 13.8%. Only 1 patient presented stenosis, and one other esophagical motor dysfunction. ConclutionS It is worth highlighting male genre, dysphagia and history of food impaction, together with history of allergy and food sensitisation. Being the disease’s natural history still unkown, doubts arise concerning the clinical handling of these patients: wether to treat symptoms alone or to persue reversion of the changes in the mucosa to prevent complications such as stenosis. Esophageal samples must have enough lamina propria and a follow-up must be made in order to find relation between remodelling and motor dysphunction in adulthood. New therapies such as topic corticoids as viscous oral budesonide, are useful. It is important to prospectively analyse the efectiveness of this therapy for long-term symptom control.

Apneas en lactantes con bronquiolitis: incidencia y factores de riesgo para un modelo de predicción

INTRODUCTION The presence of apnoea in acute bronchiolitis (AB) varies between 1.2% and 28.8%, depending on the series, and is one of its most fearsome complications. The aim of this study is to determine the incidence of apnoea in hospitalised patients diagnosed with AB, and to define their associated risk factors in order to construct a prediction model. PATIENTS AND METHOD A retrospective observational study of patients admitted to a tertiary hospital in the last 5 years with a diagnosis of AB, according to the classic criteria. Data was collected on the frequency of apnoea and related clinical variables to find risk factors in a binary logistic regression model for the prediction of apnoea. A ROC curve was developed with the model. RESULTS Apnoea was recorded during the admission of 53 (4.4%) patients out of a total 1,197 cases found. The risk factors included in the equation were: Female (OR 0.6, 95% CI: 0.27-1.37), Caesarean delivery (OR: 3.44, 95% CI: 1.5-7.7), Postmenstrual age ≤43 weeks (OR: 6.62, 95% CI: 2.38-18.7), Fever (OR: 0.33, 95% CI: 0.09-1.97), Low birth weight (OR: 5.93, 95% CI: 2.23-7.67), Apnoea observed by caregivers before admission (OR: 5.93, 95% CI: 2.64-13.3), and severe bacterial infection (OR: 3.98, 95% CI: 1.68-9.46). The optimal sensitivity and specificity of the model in the ROC curve was 0.842 and 0.846, respectively (P<.001). CONCLUSIONS The incidence of apnoea during admission was 4.4 per 100 admissions of AB and year. The estimated prediction model equation may be of help to the clinician in order to classify patients with increased risk of apnoea during admission due to AB.

Estudio de validez de una escala de gravedad de la bronquiolitis aguda para orientar el ingreso en UCIP

INTRODUCTION At present, there are few validated scoring tests for assessing acute bronchiolitis (AB) severity, and limited information on their test power. The aim of the present study is to evaluate the validity of an acute bronchiolitis severity score (ABSS) to help in deciding PICU admission. PATIENTS AND METHOD Prospective, descriptive, observational study of previously healthy infants under 1 year of age with AB, where the ABSS was used to compare severity as regards the need for PICU admission. The sample size was estimated as at least 175 patients. The research team was trained in the use of ABSS. All patients in the study were evaluated with ABSS daily, as well as in the case of clinical deterioration. The initial and maximum ABSS scores were contrasted to the need for PICU admission. A receiver operative curve was constructed, and the area under the curve was calculated, and the optimum point of sensitivity / specificity was estimated. RESULTS The study included a total of 190 patients (male / female: 58% / 42%). PICU was required in 11 (6%). The mean± SD ABSS-maximal score for patients who required and did not require PICU was 10.55± 1.12 and 6.35± 2.3, respectively (P<.001). The AUC for ABSS-maximal was 0.94 (P<.001, 95% CI: 0.90-0.98). The optimal cut-off point was set at ≥10 points for a sensitivity of 82% and a specificity of 91%. CONCLUSIONS ABSS estimates the severity of AB regarding the need for PICU admission, with a sensitivity and specificity of clinical usefulness.

Menor respuesta linfocitaria en casos graves de bronquiolitis aguda por virus respiratorio sincitial

INTRODUCTION Acute bronchiolitis (AB) of the infant has a serious outcome in 6-16% of the hospital admitted cases. Its pathogenesis and evolution is related to the response of the T lymphocytes. The objective of the present study is to determine if the lower systemic lymphocytic response is related to a worse outcome of AB in hospitalised infants. PATIENTS AND METHOD Retrospective observational-analytical study of cases-controls nested in a cohort of patients admitted due to RSV-AB between the period from October 2010 to March 2015. Those with a full blood count in the first 48hours of respiratory distress were included. Infants with underlying disease, bacterial superinfection, and premature infants <32 weeks of gestation were excluded. The main dichotomous variable was PICU admission. Other variables were: gender, age, post-menstrual age, gestational and post-natal tobacco exposure, admission month, type of lactation, and days of onset of respiratory distress. Lymphocyte counts were categorised by quartiles. Bivariate analysis was performed with the main variable and then by logistic regression to analyse confounding factors. RESULTS The study included 252 infants, of whom 6.6% (17) required PICU admission. The difference in mean±SD of lymphocytes for patients admitted to and not admitted to PICU was 4,044±1755 and 5,035±1786, respectively (Student-t test, P<.05). An association was found between PICU admission and lymphocyte count <3700/ml (Chi-squared, P=.019; OR: 3.2) and it was found to be maintained in the logistic regression, regardless of age and all other studied factors (Wald 4.191 P=.041, OR: 3.8). CONCLUSIONS A relationship was found between lymphocytosis <3700/ml in the first days of respiratory distress and a worse outcome in previously healthy infants <12 months and gestational age greater than 32 weeks with RSV-AB.Introduction: Acute bronchiolitis (AB) of the infant has a serious outcome in 6-16% of the hospital admitted cases. Its pathogenesis and evolution is related to the response of the T lymphocytes. The objective of the present study is to determine if the lower systemic lymphocytic response is related to a worse outcome of AB in hospitalised infants. Patients and method: Retrospective observational-analytical study of cases-controls nested in a cohort of patients admitted due to RSV-AB between the period from October 2010 to March 2015. Those with a full blood count in the first 48 hours of respiratory distress were included. Infants with underlying disease, bacterial superinfection, and premature infants <32 weeks of gestation were excluded. The main dichotomous variable was PICU admission. Other variables were: gender, age, post-menstrual age, gestational and post-natal tobacco exposure, admission month, type of lactation, and days of onset of respiratory distress. Lymphocyte counts were categorised by quartiles. Bivariate analysis was performed with the main variable and then by logistic regression to analyse confounding factors. Results: The study included 252 infants, of whom 6.6% (17) required PICU admission. The difference in mean ± SD of lymphocytes for patients admitted to and not admitted to PICU was 4,044 ± 1755 and 5,035 ± 1786, respectively (Student-t test, P<.05). An association was found between PICU admission and lymphocyte count <3700/ml (Chi-squared, P=.019; OR: 3.2) and it was found to be maintained in the logistic regression, regardless of age and all other studied factors (Wald 4.191 P=.041, OR: 3.8). Conclusions: A relationship was found between lymphocytosis <3700/ml in the first days of respiratory distress and a worse outcome in previously healthy infants <12 months and gestational age greater than 32 weeks with RSV-AB.