The creatine kinase (CK) test demonstrated good accuracy in screening for cases of Duchenne muscular dystrophy (DMD) in newborns, a systematic review found. The results of the review, which included 11 studies and a total of 1,416,123 newborns, were recently published in the journal Clinical Biochemistry.
“Our review demonstrated a considerably low number of DMD cases missed with CK as a screening test, even in studies with lower cut-off points. The number of recalls for diagnostic confirmation was also low,” the authors said.
The positive likelihood ratio of the CK test was superior to 10 in all the studies. The negative likelihood ratio was lower than 0.2 in 9 out of 10 studies, which suggested moderate to optimal accuracy. However, this ratio changed when considering the upper limit of the confidence interval, with only 4 studies showing a negative likelihood ratio lower than 0.2.
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The specificity of the CK test was equal to or greater than 90% in 10 studies, while sensitivity was equal to or greater than 80%. However, since 4 of the studies had wide confidence intervals due to the small sample size, only 6 out of 10 studies showed sensitivity equal to or greater than 0.7.
Moreover, the analysis of the area under the curve (AUC) of 10 studies suggested a good performance for the CK test in DMD neonatal screening (AUC, 0.9980, Q index, 0.9846).
The authors were not able to estimate the diagnostic accuracy of the CK test because the studies reported different cutoff points for CK levels, ranging from 168 UI/mL to 750 UI/mL.
Though results were promising, the authors recalled that the CK test “does not meet all the criteria for an ideal test; one of the reasons is the fact that the CK test is a secondary marker and thus, it can produce false negative tests since the level of CK in the serum is influenced by the gene expression modifying factor.”
de Freitas Nakata KC, da Silva Pereira PP, Salgado Riveros B. Creatine kinase test diagnostic accuracy in neonatal screening for Duchenne muscular dystrophy: a systematic review. Clin Biochem. Published online October 6, 2021. doi:10.1016/j.clinbiochem.2021.09.010