This prospective cohort study was done during the twelve months period from July 2015 to June 2016.
This study was done in the Pediatrics ward of C.R. Gardi Hospital (CRGH), which is a teaching hospital attached to R.D. Gardi Hospital (RDGMC), Ujjain, in the state of Madhya Pradesh, in central India. Department of Pediatrics, RDGMC has 90 beds, distributed in two wards, out of a total of 630 beds in CRGH. A six-bedded pediatric intensive care unit is also attached to the department.
During the study period, the Department of Pediatrics had three units, each having 30 beds, distributed in two wards. Each unit had at least three residents and teaching faculty consisting of a professor, an associate professor, and an assistant professor. The experience of each professor was a minimum of 8 years and that of associate professor and assistant professor at least 5 and 3 years respectively.
Selection of the participants
Consecutive patients aged between 3 months to 5 years, admitted for fever and having an axillary temperature of 100°F (37.7 0C) or more taken with mercury thermometer at the time of admission were included in the study. Children admitted with fever but having chronic co-morbidities: malignancy, renal failure, hepatic failure, congestive cardiac failure, and bone marrow aplasia, children on immunosuppressive drugs such as steroids, and HIV positive children were not included in the study. Children transferred-in with fever from other hospitals with a diagnosed bacterial infection or a laboratory result suggestive of bacterial infection were not included, as it would not have allowed an independent clinical assessment of cases. Children with osteomyelitis, cellulitis and patients with surgery and trauma were not included as these children are routinely admitted in wards other than pediatrics.
All the admitted patients were screened for eligibility by the pediatric resident on-call as soon as possible after admission. The details of the study were discussed with the mother or caregiver accompanying the child fulfilling the inclusion criteria and a written consent obtained. After obtaining consent, a standardized pre-defined questionnaire containing clinical history and physical examination was filled in. The questionnaire also contained epidemiological, clinical, hematological and biochemical parameters of the cases. Patients were provided immediate routine or intensive care as per the department protocol. A senior consultant examined all patients within 24 hours of admission. Investigations were done at the discretion of the senior consultant.
The definitions used in the study are provided in supplementary Table1.
The unit of analysis was the child and not the number of febrile episodes. The primary outcome was proportion of children having SBI among the children presenting with fever. The presence of SBI was confirmed by presence of at least one of the following criteria: 1) blood culture positive; 2) a child was considered to have bacterial pneumonia: if the child presented with breathlessness and had blood culture positive or if along with breathlessness, chest X-ray showed consolidation and C-reactive protein (CRP) value was more than 1000µg/dl . X-ray chest were reported by a radiologist not part of the study; 3) a child was considered to have UTI if in a toilet trained child with suspected UTI midstream clean catch urine sample was culture positive and in non-toilet trained children with suspected UTI urine obtained by transurethral bladder catheterization was culture positive; all children were screened for UTI using urine microscopy done on a spun urine sample within two hours of collection, with 5 or more white blood cells per high power field. 4) a child was diagnosed to have enteric fever when presentation was fever with malaise, headache, abdominal discomfort, coated tongue and Widal test positive with somatic antigen (O) and flagellar antigen (H) titers greater than 320 or blood culture was positive for S. typhi; 5) a child was considered to have bacterial meningitis in presence of clinical features suggestive of meningitis, with either blood culture and/or cerebrospinal fluid culture was positive. A fever was labeled as “no confirmed bacterial infection” when the above diagnosis was ruled out, thus viral fever was a diagnosis of exclusion. The secondary outcome was to determine the epidemiological, clinical, hematological, and biochemical risk factors associated with SBI.
Two milliliter (ml) of blood was obtained for hematological and biochemical investigations and 3-4 ml to 10 ml for blood culture according to child’s age. The following investigation were done for all children included in the study: a) complete blood count done using five-part automated coulter counter using fluorescence flow cytometry (XS-800i, Sysmex India Pvt. Ltd, India). Peripheral smear examination was done for leucocyte morphology, immature to mature cell ratio and toxic granules, malaria parasite (thick and thin smear) and red cell morphology; b) a quantitative C- reactive protein (CRP) (Vitros CRP slides, Vitros 250 Chemistry Analyzer, Ortho Clinical Diagnostics, Johnson & Johnson, USA); c) serum electrolytes: serum sodium, potassium, and calcium (Vitros 250 Chemistry Analyzer, Ortho Clinical Diagnostics, Johnson & Johnson, USA); d) Widal test was done using slide and tube agglutination test (Febrile Antigen Set, Span Diagnostic Ltd., India); e) blood and cerebrospinal fluid (CSF) culture was collected under sterile conditions in Bactec Peds Plus/F vial® and pathogens were isolated using the automated BacT/ALERT system (bio-Mérieux, Inc., Marcy l’Étoile, France); e) Urine cultures were done for urine samples having with 5 or more white blood cells per high power field on urine microscopy-urine sample was inoculated into the Blood Agar plate and Mac-Conkey agar plate using the semi quantitative method and incubated aerobically at 37°C for 24 hours. A 0.5 McFarland suspension was prepared from pure culture of uro-pathogens in a nutrient broth and inoculated on Muller-Hinton agar. Antimicrobial susceptibility testing for blood and urine cultures was done using the Kirby Bauer disk diffusion method and results interpreted according to 2018 Clinical and Laboratory Standards Institute guidelines . Extended-spectrum β-lactamase (ESBL) production was detected using a double-disc synergy test . Multidrug-resistant isolates were defined as isolates having co-resistance to at least three antibiotic groups . For all children with probable intrathoracic tuberculosis we collected gastric aspirate and induced sputum samples on 2 consecutive days. All samples were subjected to smear examination after Ziehl-Neelsen staining. An aliquot of each sample was tested using Xpert MTB/RIF assay.
Sample size calculation
The proportion of SBI is known to vary between 24 to 40%, according to geographical area and the age of children [18, 19]. We choose a proportion of 30% from above studies to calculate the sample size. Sample size calculation was done to detect at least 15% difference around proportion of 0.30, with a power of 90 and two-sided alpha of 0.05. The estimated minimum sample size needed was 230 children. Assuming that 20% children will not be able to complete investigations for fever we increased the sample size by a similar proportion to 276 (230×0.2).
Data was entered in EpiData Entry (Version 3.1, Epi Data Software Association, Odense Denmark) and statistical analyses was performed using Stata (Version 13.0 Statacorp. Texas, USA). For continuous variables range, mean and standard deviation (SD) are presented. Categorical independent variables were investigated using Pearson chi-square with the dependent variable being SBI (yes/no). In case of cell count less than five or at least one cell-count equal to zero, the variable was excluded for further analyses. Pearson Chi-square test was used to test for each risk factor’s association with SBI.
A generalized linear regression model was used to examine the association of independent risk factors responsible for SBI. The independent risk factors were compared between neonates with and without SBI (binary outcome variable). The adjusted relative risk (RR) of SBI was calculated using multivariate predicted marginal proportions for logistic regression models and included the following independent variables as covariates: sex—male versus female; age—in months as continuous; partially immunized child—yes versus no; breathlessness—yes versus no; weight loss—yes versus no; and suspected UTI—yes versus no. The means along with the associated 95% confidence intervals (CI) and P values were reported from GLMs. A P value of <0.05 was considered significant in the final model. For the final model, model discrimination was done using C-statistics.
The Institutional Ethical Committee approved the study (Approval number IEC Ref No 461/2015). The procedures followed were in accordance with the ethical standards set by the institutional ethics committee and with the Declaration of Helsinki.