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Neonatal jaundice

of a diagnostic test, sensitivity, specificity and positive and negative predictive values (PPVs and
NPVs) were calculated or quoted where possible (see Table 2.3).

Table 2.3 ‘2 × 2’ table for calculation of diagnostic accuracy parameters
Reference standard positive Reference standard negative Total
Test positive a (true positive) b (false positive) a+b
Test negative c (false negative) d (true negative) c+d
Total a+c b+d a+b+c+d = N (total
number of tests in study)
Sensitivity = a/(a+c), specificity = d/(b+d), PPV = a/(a+b), NPV = d/(c+d)

The system described above covers studies of treatment effectiveness. However, it is less
appropriate for studies reporting accuracy of diagnostic tests. In the absence of a validated
ranking system for this type of test, NICE has developed a hierarchy of evidence that takes into
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account the various factors likely to affect the validity of these studies (see Table 2.4).

Table 2.4 Levels of evidence for studies of the accuracy of diagnostic tests
Level Type of evidence
a
b
Ia Systematic review (with homogeneity) of level-1 studies
Ib Level-1 studies
b
c
II Level-2 studies ; systematic reviews of level-2 studies
d
III Level-3 studies ; systematic reviews of level-3 studies
IV Consensus, expert committee reports or opinions and/or clinical experience without
explicit critical appraisal; or based on physiology, bench research or ‘first principles’
a Homogeneity means there are minor or no variations in the directions and degrees of results between individual
studies that are included in the systematic review.
b Level-1 studies are studies that use a blind comparison of the test with a validated reference standard (‘gold’ standard)
in a sample of patients that reflects the population to whom the test would apply.
c Level-2 studies are studies that have only one of the following:
• narrow population (the sample does not reflect the population to whom the test would apply)
• use a poor reference standard (defined as that where the ‘test’ is included in the ‘reference’, or where the ‘testing’
affects the ‘reference’)
• the comparison between the test and reference standard is not blind
• case–control studies.
d Level-3 studies are studies that have at least two or three of the features listed above.

Clinical evidence for individual studies was extracted into evidence tables (see Appendix H)
and, where possible, quantitative synthesis (meta-analysis) was carried out. If no meta-analysis
was possible, a brief summary of each study was included in the guideline text. If an analysis
was carried out, the results may be presented pictorially (i.e. forest plots, summary ROC curves)
as well as in the text. If no meta-analysis was carried out, the results from each included study
are reported in the text and, where appropriate, in summary tables. The body of evidence
identified for each clinical question was synthesised qualitatively or quantitatively in clinical
evidence statements that accurately reflect the evidence.
Lists of excluded studies for each clinical question are presented in Appendix J.

Specific considerations for this guideline
For this guideline, the effectiveness of interventions was assessed against the following outcome
domains:
● serum bilirubin concentrations (change from baseline)
● duration of treatment
● treatment failure
● adverse effects
● mortality.

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