Page 61 - 15Diarrhoeaandvomiting

Diarrhoea and vomiting caused by gastroenteritis in children under 5 years

children had symptoms of vomiting, diarrhoea more than three episodes and fever and underwent
laboratory testing. Exclusion criteria were not defined. Bacterial aetiology was determined by
stool culture while antigen testing was used to isolate rotavirus, but it was done in only 28
children. QR-CRP was performed at the bedside with a level of 8 mg/l or more considered as a
positive test. Stool culture was positive for bacteria in eight children while rotavirus was isolated
in 13 children. The mean CRP concentration was significantly higher in children with bacterial
gastroenteritis than in those with viral gastroenteritis (P < 0.001). The ROC curve was used to
calculate the diagnostic accuracy of QR-CRP. The best cut-off value derived from the ROC curve
was 95 mg/l and, at this cut-off value, QR-CRP showed a sensitivity of 87%, specificity of 92%
and AROC of 0.94 in detecting bacterial gastroenteritis. [EL = 3]
Another study from Israel evaluated the ability of total and differential leucocyte counts to
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differentiate bacterial from non-bacterial gastroenteritis infections. This study recruited 238
children admitted to hospital with gastroenteritis but further details about demographic
characteristics were not specified. Bacterial pathogens were isolated by stool culture, along with
testing for blood counts but no further details were provided about these tests. One hundred and
ninety-two children had bacterial gastroenteritis (shigella in 130, salmonella and campylobacter
in 25 each and E. coli in 12) while 46 children were in the non-bacterial group. The total white
blood counts were similar between the aetiological groups but great variation was observed in the
differential blood counts. The absolute band neutrophil count and the ratio of band neutrophils to
total neutrophils were significantly higher in the shigella, salmonella and campylobacter groups
compared with the E. coli and non-bacterial groups (P < 0.05 for all comparisons). Among all the
bacterial pathogens, children with shigella had the highest values for both these parameters. It
was found that band neutrophils to total neutrophils ratio of more than 0.10 could differentiate
bacterial infections from E. coli and non-bacterial groups with a sensitivity of 84% and a specificity
of 75%. [EL = 3]

Evidence summary

There was a lack of good-quality studies to evaluate the ability of laboratory tests to distinguish
between bacterial and viral gastroenteritis. Evidence from three studies suggested that raised CRP
levels had a high diagnostic ability in detecting bacterial causes, with AROC ranging between
0.83 and 0.94, but the studies used different cut-off values to define a positive CRP test. Other
acute-phase proteins (IL-6 and IL-8) and raised ESR levels were found to be less accurate than
CRP. The total leucocyte blood count was not helpful in distinguishing bacterial from non-
bacterial/viral causes in two studies, while one study reported raised absolute neutrophil band
cell count and the ratio of band neutrophils to total neutrophils count (ratio > 0.10) to be useful
in distinguishing between the pathogens.

GDG translation from evidence to recommendations
There was evidence that in children with gastroenteritis an elevated CRP would support a
diagnosis of bacterial rather than viral gastroenteritis. However, a normal CRP does not exclude
the possibility of bacterial gastroenteritis. As discussed elsewhere (Chapter 7 on antibiotic
therapy), in the UK most children with bacterial gastroenteritis do not require antibiotic treatment.
However, infants younger than 6 months and immunocompromised children should be treated
with antibiotics if they have salmonella gastroenteritis. In such vulnerable patients if bacterial
gastroenteritis is clinically suspected, antibiotic therapy should be commenced while awaiting
the results of stool microbiological investigations. It would not be safe to withhold antibiotic
treatment based on a normal CRP result. As measurement of the CRP would rarely influence
management, the GDG did not consider that its routine use would be cost-effective.
The GDG considered that, in keeping with normal clinical practice, a blood culture (the gold
standard for septicaemia) should be performed prior to commencing antibiotic therapy in children
with suspected or confirmed bacterial gastroenteritis.
Children with E. coli O157:H7 infection are at risk of developing HUS and the GDG considered
that these children should be monitored for the development of microangiopathic haemolytic
anaemia, thrombocytopenia and renal insufficiency. This should be done in consultation with an
appropriate specialist.

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