Research in context
Evidence before this study
We reviewed relevant English language studies by searching PubMed for the terms “ADAMTS13”, “score”, and “clinical prediction tool”. We identified two studies that reported diagnostic scoring systems for severe ADAMTS13 deficiency. One was derived from a national registry experience whereas the other utilised a small single-centre case series. Neither score was validated externally or shown to add value to clinical practice.
Added value of this study
We report a clinical prediction tool for severe ADAMTS13 deficiency that was derived in a multicentre consortium and validated externally using a dataset assembled at a separate institution. This scoring system includes historical and laboratory variables that would be obtainable rapidly in a wide range of clinical settings. We showed the superiority of our prediction score to a previously proposed diagnostic score for thrombotic microangiopathy and assessed directly the potential contribution of our scoring system to clinical practice using three independent metrics.
Implications of all the available evidence
Profound thrombocytopenia associated with normal or mildly impaired renal function in patients presenting with thrombotic microangiopathy is predictive of severe ADAMTS13 deficiency. Our results indicate that a seven-component clinical prediction score containing platelet count and measures of renal function is appropriate for use in settings in which ADAMTS13 activity testing might not be available readily and that our scoring system represents an improvement over use of clinical assessment alone.