Study designs of evaluations included in the review
The inclusion criteria were not explicitly defined in terms of study design. The use of the keyword 'diagnosis' implied that diagnostic studies were sought.
Specific interventions included in the review
Studies of 'new' laboratory tests (excluding haematological tests and acute phase C-reactive protein) that focused on serious bacterial infections were eligible for inclusion. The specific tests used in the included studies were: interleukin-6, interleukin-8, interleukin-1 receptor antagonist, tumour necrosis factor (TNF)-alpha, fibronectin levels, neutrophil elastase inhibitor level, neutrophil CD11B level, polymerase chain reaction, procalcitonin level, TNF-receptor p55 and p75 levels, and soluble intracellular adhesion molecule level. Some studies used a combination of more than one test.
Reference standard test against which the new test was compared
The studies had to compare new' tests with proven serious bacterial infections diagnosed using standard criteria. Only studies that used unequivocal proof of bacterial infection (bacterial growth) in cultures from central nervous system fluid, or blood from sterile sites, were included. Studies of clinical sepsis (defined as not meeting criteria for infection), urinary tract infections and studies of antenatal tests were excluded. Studies reporting ante- and postnatal infection were only included if they presented separate data for neonatal patients. The included studies used different cut-off values to diagnose the presence of infection. The review used the authors' own cut-off values where these were reported.
Participants included in the review
Studies of newborns with a postnatal age of less than 90 days were eligible for inclusion. The included studies were of infants with gestational age (where reported) ranging from 23 to 44 weeks
Outcomes assessed in the review
The inclusion criteria were not specified in terms of outcomes. The outcomes measured in the included studies were the sensitivity, specificity, and positive and negative likelihood ratios (LRs).
How were decisions on the relevance of primary studies made?
Two reviewers independently selected studies for inclusion and resolved any disagreements through discussion with a third reviewer. The kappa statistic was used to assess inter-reviewer agreement.