Lee et al noted that a recent study had found that an initial curve of 25 degrees or above is 24 times more likely to progress to beyond 30 degrees (treatment threshold) than an initial curve below 25 degrees, but added: “The large hazard ratio indicates room for refined classification, and the use of only factor in prediction suggesting the possibility of improvement through the tandem use of multiple prognostic factors.”
Thus, the authors aimed to develop a “more refined, practical, user-friendly clinical decision rule” for evaluating the risk of progression in patients with AIS. They examined curve progression data, from a retrospective analysis, for 1,464 patients who met the selection criteria: aged 10 years or older at first presentation, untreated, riser sign of 2 or below, and an initial Cobb angle of less than 30 degrees.
A univariable analysis confirmed existing data by indicating that girls are more likely to progress than boys, the risk of progression decreases with age and height, and increases with initial curvature.
However, in a multivariable analysis, Lee et al found that presenting age was significantly more influential in girls than in boys and that the risk associated with age decreased with increasing initial curvature (to the point that the associated adjusted hazard ratio became closer to one). They reported: “Our study has incorporated interacting factors and showed that age did not have much influence in larger curves, which are already at high risk of progression, and in mild curves, which are on the other hand at lower risk of progression.”
Furthermore, as a result of their analysis, Lee et al were able categorise patients into one of four risk categories. They said: “The highest risk group, group IV, consisted of subjects who had an initial risk curvature of at least 26 degrees and had a 7.8-fold higher risk than the lower risk group, group I, which comprised of subjects who had an initial curvature of less than 18 degrees.” The investigators claimed that, using their four identified groups, different management schemes can be designed, stating: “For instance, patients assessed to a higher risk group may be followed up more frequently, whereas patients classified as having a lower risk may be managed less frequently or have fewer X-rays to reduce unnecessary exposure to radiography. Patients that fall into the lowest risk group may even be monitored through telephonic interviews instead of clinical visits. These arrangements would optimise the use of resources.”
They added that while a DNA-based prognostic test (as shown in a recent study) would be “very useful in identifying progressive curve”, it has not been completely validated and, at present, is “relatively expensive”. Lee et al concluded: “We believe before genetic markers are completely validated and the price becomes affordable, classification by clinical parameters is still the most practical useful means.
Daniel Fong, one of the lead authors, School of Nursing, The University of Hong Kong, Pokfulam, Hong Kong SAR, said: “The new risk classification rule may help to optimize the frequency of follow up radiologic monitoring thus avoiding unnecessary X-ray exposure to these young children.’