2.1. Materials
Clinical data of children infected with norovirus admitted to the the Department of Emergency of Guangzhou Women and Children′s Medical Center between January 2019 and January 2020 were retrospectively collected and divided into two groups: the CwG group and acute gastroenteritis group. Clinical data of children diagnosed with febrile seizures at the same time were also included in our study to rule outing post-convulsive effects[4]. Clinical and related laboratory data of enrolled children were analysed retrospectively.
2. 2. Inclusion and exclusion criteria
2.2.1. The inclusion and exclusion criteria for CwG
The inclusion criteria for CwG were as follows[5、6]: (1) previously healthy infants aged 6 months to 3 years; (2) mild gastroenteritis with convulsions, none to mild dehydration, and no apparent acid-base balance or electrolyte disorder; (3) none to low-grade fever (body temperature < 38.0℃) during convulsions; (4) no epileptiform discharge on the interparoxysmal electroencephalogram, no apparent abnormality in the skull when assessed by computerized tomography/magnetic resonance imaging, and normal blood glucose, blood calcium, blood magnesium, and cerebrospinal fluid levels; and (5) stool samples positive for norovirus by reverse transcription polymerase chain reaction (RT-PCR). The exclusion criteria were as follows: (1) intracranial infection, encephalopathy, or cerebral trauma related to convulsions; (2) mental or neurological defects; and (3) intestinal bacterial infection (such as a positive stool culture). For patients who were hospitalized more than once during our study period, only data from the first diagnosis was included.
2.2.2. Diagnostic criteria for febrile seizures
According to the latest guidelines[7], febrile seizures are those that occur in a child 6 months to 5 years of age and are accompanied by a fever (≥ 100.4°F [38°C]), without any central nervous system infection or other encephalopathies. They may be classified as simple or complex. Complex seizures last ≥ 15 minutes and are associated with focal neurologic findings or recur within 24 hours; however, they exclude moderate to severe dehydration and severe electrolyte imbalances.
2.2.3 The inclusion and exclusion criteria for acute gastroenteritis
The inclusion criteria for simple gastroenteritis were as follows: children with gastrointestinal symptoms caused by acute gastroenteritis, no serious dehydration and acidosis, no electrolyte imbalance, and no low blood sugar levels. We excluded intracranial space-occupying lesions and other diseases that cause vomiting, diarrhoea, and other gastrointestinal symptoms from this study. We also excluded patients with serious complications and moderate-to-severe dehydration, defined by the World Health Organization as a fluid deficit of > 5% of body weight [8],See Table 1 for details .
2.2.4. Clinical and laboratory data
Clinical data on the age at onset, sex, timing and frequency of diarrhoea and seizures, and past medical history, such as for epilepsy and congenital central nervous system disease were collected. Laboratory findings, including C-reactive protein(CRP); Lac lactate; neutrophil elastase(NE); white blood cell(WBC),creatine kinase myocardial band(CKMB);uric acid, sodium, potassium, chloride, calcium, magnesium, glucose,potential of hydrogen(PH),bicarbonate (HCO3–), bases excess(BE),blood urea nitrogen, and creatinine levels were reviewed to exclude patients with an electrolyte imbalance or hypoglycaemia, which may also cause seizures. Other tests include a cranial MRI, a cranial CT, and an electroencephalogram.Laboratory tests were performed at the time of visiting the emergency room (after at least one seizure) in most cases.
2.3. Methods
Faecal samples were tested for norovirus by RT-PCR using a norovirus RNA Detection Kit (Guangdong Huayin Medicine Science, Co. Ltd. Guangzhou, China). An elevated serum uric acid level was defined as > 420 μmol/L, which was determined by colorimetry (Uric Acid Test Kit (manufacturer: Roche Diagnostics GmbH; Production address: Sandhofer Strasse16,68305 Manneim, Germany). All statistical analyses were performed using the IBM SPSS version 21.0. Age was expressed as median and range, continuous variables (seizure frequency and clinical laboratory indicators, such as serum uric acid, myocardial enzymes, creatinine, blood glucose, HCO3-, calcium, sodium, and potassium levels) as mean ± standard deviation and categorical variables as N (%). For homogeneity of variance, a t-test was used to compare the two groups, while the Mann–Whitney U test was used for comparison between non-normally distributed data groups. Statistical significance was set at P < 0.05. Spearman’s rank-order correlation was used for correlation analysis. A receiver operating characteristic (ROC) analysis was performed to calculate the area under the curve (AUC) for ROC and the serum uric acid cut-off value that optimally distinguished CwG from acute gastroenteritis patients. The optimal threshold value corresponded to the best sum of sensitivity and specificity.