Chest radiographs may help diagnose ADA-SCID early
Published Date: 3/2/20Access Full Text Article
medwireNews: Skeletal abnormalities visible on chest radiographs may help to distinguish adenosine deaminase-deficient severe combined immunodeficiency (ADA-SCID) from other forms of SCID in infants, suggests a chart review.
The abnormalities in question include squaring or spurring of the inferior scapular angle and cupping of the costochondral junctions.
“Recognition of these radiological features should trigger focused diagnostic investigations leading to early recognition of ADA deficiency in a child with suspected immunodeficiency”, say Alistair Calder and colleagues from Great Ormond Street Hospital for Children in London, UK.
They caution, however, that these features could be used to reliably diagnose ADA-SCID only in children aged around 7 months or younger, as the abnormalities “disappear around the 7th month of life”.
The analysis included 36 children with ADA-SCID (median age at presentation, 3.1 months) and 25 children with other forms of SCID (median age at presentation, 4.8 months) who were treated at a tertiary immunology centre between 2000 and 2017, and had assessable chest radiographs.
Three radiologists with varying levels of experience evaluated the chest radiographs for the presence or absence of scapular squaring, scapular spurring and costochondral cupping, and diagnosed ADA-SCID with an average sensitivity of 62.9% and average specificity of 82.9%.
An area under the receiver operating characteristics curve analysis showed that “the optimal threshold for test performance” was at 7.3 months, say the study authors, with average sensitivity and specificity values of 91.7% and 80.7%, respectively, at or below this cutoff, and of 10.9% and 88.9% above the cutoff.
Taken individually, the positive likelihood ratio at 7.3 months or younger was highest for scapular spurring, at 54.6, whilst the ratios for costochondral junction cupping and scapular squaring were 7.8 and 4.0, respectively.
Writing in the Journal of Clinical Immunology, Calder and team highlight that “the threshold of 7.3 months is not a hard cut-off, and for clinical purposes, the disappearance of the features should be expected around 7 months.”
They note that all patients received treatment for ADA-SCID, “which may relate to the disappearance of radiological features”, but stress that a definitive explanation for the loss remains elusive.
The authors additionally report that the inter-reader agreement was good for the whole cohort and for the subgroup aged 7.3 months or younger, with kappa values of 0.741 and 0.709, respectively, but was moderate for the subgroup that was older than 7.3 months, at 0.434.
Moreover, the test was valid “both for senior paediatric radiologists and for a junior paediatric radiologist with no prior knowledge of ADA-SCID when allowed to study the relevant literature”, the team concludes.
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