Adoption in Canada of International Risk Scoring Tool to Predict Respiratory Syncytial Virus Hospitalization in Moderate-to-Late Preterm Infants (32–35 Weeks’ Gestational Age)

Introduction The advisory board to the Ontario Ministry of Health is considering adoption of the new three-variable International Risk Scoring Tool (IRST), which used data pooled from six observational studies (including PICNIC from Canada) to predict RSVH in 32 to 35 wGA infants (Blanken. PediatrPulmonol2018;53:605–12). Canada is currently using a seven-variable RST developed solely from PICNIC focused on 33 to 35 weeks’ gestational age (wGA) infants (Sampalis. Med Decis Making 2008; 28:471–80]. We explored the potential implications of switching from the Canadian to the IRST.

Materials and Methods The two RSTs were compared for included risk factors and predictive accuracy (area under the receiver operating characteristic curve). Correlations (Spearman rank) between cut-off scores for low-, moderate-, and high-risk subjects were assessed against the pooled dataset using infants born 33 to 35 wGA with complete data for all risk factors in both RSTs.

Results Please refer to [Table A012] for a summary of main results. In details, the two RSTs contain many of the same risk factors (birth proximity to the RSV season, smoking, siblings, and day care), with the Canadian RST also including sex, small for GA, and familial eczema. Predictive accuracy of the two RSTs is similar (AUROC, IRST: 0.773 [sensitivity: 68.9%; specificity: 73.0%] vs. Canadian: 0.762 [68.2%; 71.9%]). Significant correlations between cut-off scores (p < 0.001) and risk categories (p < 0.001) were apparent, although the correlation coefficients were weak for both (scores: 0.217; categories: 0.055). While the proportion of high-risk infants was similar for the two RSTs (IRST: 0.6% vs. Canadian: 0.7%), a far greater number of infants were assigned moderate-risk by the IRST (19.9% vs. Canadian: 9.8%).

Conclusion The IRST can be considered a simpler model (few risk factors) than the Canadian RST, but assigns more infants as moderate-risk. Combined with including 32 wGA infants, adoption of the IRST in Canada has cost-effective implications for RSV prophylaxis which warrants further investigation.

Table A012

RST	n	Score	Number in each risk category
			High	Moderate	Low
	4,529	0–100	27 (0.6%)	443 (9.8%)	4,059 (89.6%)
Canadian
Small (<10th percentile) gestational age (yes or no)
Sex (male vs. female)
Born during RSV seasona
Family history of eczema (yes or no)
Subject or siblings attending day care (yes or no)
>5 individuals in the home, including subject (yes or no)
>1 smoker in the household (yes or no)
RSVH rate (%)			11.2%	4.3%	1.0%
IRST	4,529	0–56	31 (0.7%)	902 (19.9%)	3,596 (79.4%)
Birth 3 months before and 2 months after season start date (yes or no)
Smokers in the household and/or while pregnant (neither, either, or both)
Siblings (excluding multiples) and/or (planned) day care (neither, either, or both)
RSVH rate (%)			9.5%	3.3%	1.0%

Abbreviations: IRST, international RST; RST, risk scoring tool; RSVH, respiratory syncytial virus hospitalization.

^a November–January.

Conflict of Interest

None declared.