Why refer to the National aHUS Service

The National aHUS Service

The National aHUS Service offers a complete diagnostic toolkit to assess a potential new case of aHUS. This helps to rapidly and reliably exclude ADAMTS13 deficiency (TTP), STEC-HUS and other secondary causes of aHUS.

The National aHUS Service is then able to offer treatment to patients who are likely to have aHUS as early as clinically appropriate to maximise the chances of recovery of renal function.

Differentiating ADAMTS13 deficiency (and other causes of HUS): When aHUS is suspected, the first critical diagnostic step is to exclude ADAMTS13 deficiency. We recognise the importance of prompt use of plasma exchange until ADAMTS13 deficiency has been excluded.

For further guidance see https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2141.2012.09167.x

Diagnosis

To help reduce any diagnostic uncertainty, we recommend all samples relating to the possible diagnosis of ADAMTS13 deficiency, STEC-HUS and complement-mediated aHUS are taken prior to plasma exchange.

We therefore encourage EARLY REFERRAL to the National aHUS Service to access our diagnostic toolkit (that includes 7-days a week ADAMTS13 testing) even before (though not delaying) ADAMTS13 testing and initial plasma exchange.

Timing of treatment with eculizumab /ravulizumab

With respect to the timing of eculizumab/ravulizumab in a possible case of aHUS, and prior to the exclusion of ADAMTS13 deficiency, our recommendations are in accordance with KDIGO guidelines:

In adults, we recommend that plasma therapy is undertaken until ADAMTS13 deficiency has been reliably excluded.
In children, it may be possible to commence eculizumab/ravulizumab prior to the availability of the ADAMTS13 activity result.

In all cases, early referral to the National aHUS Service allows timely clinical discussion, investigations and decision making.

Please note: The decision to initiate Eculizumab or Ravulizumab (following exclusion of ADAMTS13 deficiency) may be made prior to the availability of diagnostic tests that would support a diagnosis of STEC-HUS or a secondary TMA.

A decision to await additional diagnostic tests before commencing Eculizumab/ Ravulizumab will depend on the clinical presentation, with the ultimate aim to maximise clinical efficacy in patients who subsequently are confirmed to have primary complement mediated aHUS.

There is currently no evidence as to the efficacy of Eculizumab/Ravulizumab in STEC–HUS or secondary TMAs and consequently NHS England do not fund its use in this situation.

Therefore in some cases where initial doses of Eculizumab have been given, additional doses are not authorised once confirmation of an alternative diagnosis has been made.

Why refer to the National C3G Service

Access to Eculizumab for patients with aHUS