Prediction of Upper Respiratory Illness Using Salivary Immunoglobulin A in Youth Athletes
in International Journal of Sports Physiology and PerformancePurpose: To evaluate the relative importance and predictive ability of salivary immunoglobulin A (s-IgA) measures with regards to upper respiratory illness (URI) in youth athletes. Methods: Over a 38-week period, 22 youth athletes (age = 16.8 [0.5] y) provided daily symptoms of URI and 15 fortnightly passive drool saliva samples, from which s-IgA concentration and secretion rate were measured. Kernel-smoothed bootstrapping generated a balanced data set with simulated data points. The random forest algorithm was used to evaluate the relative importance (RI) and predictive ability of s-IgA concentration and secretion rate with regards to URI symptoms present on the day of saliva sampling (URIday), within 2 weeks of sampling (URI2wk), and within 4 weeks of sampling (URI4wk). Results: The percentage deviation from average healthy s-IgA concentration was the most important feature for URIday (median RI 1.74, interquartile range 1.41–2.07). The average healthy s-IgA secretion rate was the most important feature for URI4wk (median RI 0.94, interquartile range 0.79–1.13). No feature was clearly more important than any other when URI symptoms were identified within 2 weeks of sampling. The values for median area under the curve were 0.68, 0.63, and 0.65 for URIday, URI2wk, and URI4wk, respectively. Conclusions: The RI values suggest that the percentage deviation from average healthy s-IgA concentration may be used to evaluate the short-term risk of URI, while the average healthy s-IgA secretion rate may be used to evaluate the long-term risk. However, the results show that neither s-IgA concentration nor secretion rate can be used to accurately predict URI onset within a 4-week window in youth athletes.
Sawczuk, Jones, Beggs, Scantlebury, and Till are with the Inst for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom. Sawczuk is also with Queen Ethelburga’s Collegiate, Thorpe Underwood, York, United Kingdom. Jones and Till are also with Yorkshire Carnegie Rugby Club, Emerald Headingley Stadium, Leeds, United Kingdom; and with Leeds Rhinos Rugby Club, Headingley Carnegie Stadium, Leeds, United Kingdom. Jones is also with the Rugby Football League, Red Hall, Leeds, United Kingdom. Jones and Welch are with the School of Science and Technology, University of New England, Armidale, NSW, Australia.
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