The Association between Serum Bilirubin and Kernicterus Spectrum Disorder: A Systematic Review and Meta-Analysis.

BACKGROUND Total serum bilirubin (TSB) is used in managing neonates with jaundice, but clear evidence on its association with major outcomes is lacking. OBJECTIVES We evaluated the association between TSB and kernicterus spectrum disorder (KSD). METHODS We searched PubMed, EMBASE, and CENTRAL till July 2021. Two authors independently selected relevant cohort studies, extracted data (CHARMS checklist), assessed risk of bias (RoB) (QUIPS tool), and rated certainty-of-evidence (Grades of Recommendation, Assessment, Development, and Evaluation). We pooled adjusted odds ratio (aOR) (random-effect) via generic inverse variance methods. RESULTS From 2,826 records retrieved, we included 37 studies (n = 648,979). Fifteen studies had low, 16 moderate, and 6 high RoB, with majority having concerns on confounder adjustment and statistical analysis. Twenty-two studies contributed meta-analysis data, and 15 were summarized narratively. TSB appears associated with KSD in infants with certain risk factors (aOR 1.10, 95% CI: 1.07-1.13; 5 studies [n = 4,484]). However, TSB (aOR 1.10, 95% CI: 0.98-1.23; 1 study [n = 34,533]) or hyperbilirubinemia (aOR 1.00, 95% CI: 0.51-1.95; 2 studies [n = 56,578]) have no clear association with kernicterus or neurological diagnosis in overall neonatal population (moderate-certainty-evidence). One study shows that infants with hyperbilirubinemia appear likelier to develop attention-deficit disorder (aOR 1.90, 95% CI: 1.10-3.28) and autistic spectrum disorder (aOR 1.60, 95% CI: 1.03-2.49, n = 56,019) (low-certainty-evidence). Certain clinical factors appear associated with KSD, although very few studies contributed to the analyses. CONCLUSIONS Despite the importance of this question, there is insufficient high-quality evidence on the independent prognostic value of TSB for adverse neurodevelopmental outcomes in most neonatal populations. Future studies should incorporate all known risk factors alongside TSB in a multivariable analysis to improve certainty-of-evidence.