Table 3 Sensitivity, specificity and positive predictive value (PPV) for several referral rules for between postnatal days 3 and 11.

Test	Sensitivity (%)	Specificity (%)	PPV (%)
10%	90.4	98.3	3.7
−2.5 SDS	85.5	99.4	9.2
−2 SDS	90.4	97.7	2.7
−2.5 SDS 3–6 days	85.5	99.4	9.2
and 10% 7–11 days