Local code : ACRA

Preferred Sample Type

Acetylcholine receptor antibodies (ACRA)

Suitable Specimen Types

  • Serum
  • EDTA Plasma
5 mL (300 uL minimum volume of serum/plasma)

Sample Processing in Laboratory


Sample Preparation

Centifruge and separate. 300 uL of sample either serum or EDTA plasma is necessary to allow duplicate analyses to be carried out if required. Grossly haemolysed or lipaemic samples are unsuitable for this assay.

Turnaround Time

21 days

Sample Stability

Samples are stored frozen until analysis is complete and subsequently stored in Immunology for 6 months.

Acetylcholine receptor antibodies (ACRA)

General Information

Autoantibodies to the acetylcholine receptor (ACh RAb) are responsible for failure of the neuromuscular junction in myasthenia gravis, and measurement of the antibodies can be of considerable value in disease diagnosis.

As of 01/10/2021 this assay is performed on automated ELISA platform rather than by radioimmunoassay .

This assay has a stated sensitivity of 96% and a specificity of 97.1%


Patient Preparation



About 10% patients with myasthenia may have no detectable ACR abs.

 Up to 40% of Patients with exclusively ocular myasthenia may have negative ACR abs.

In cases where ACR antibodies are negative and clinical presentation and suspicion of myesthenia remain high it is recommended that  a repeat sample is sent and a request for ACR cluster antibodies by cell based assay is made.

Reference Range

<0.4 nmol/L = negative.

0.4 - 0.5 nmol/L = borderline

>0.5 nmol/L = positive.

Reference range provided by Kit manufacturer



  • EQA Scheme?: Yes
  • EQA Status: UKNEQAS

The laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital form part of the services provided by University Hospitals Birmingham and are UKAS (United Kingdom Accreditation Service) accredited to the ISO 15189:2012 standard. For a list of accredited tests and other information please visit the UKAS website using the following link:

  • Heartlands, Good Hope and Solihull Hospital pathology laboratories are a UKAS accredited medical laboratory No.8217
  • United Kingdom Health Security Agency laboratory is a UKAS accredited medical laboratory No.8213

Tests not appearing on the UKAS Schedule of Accreditation currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further test information, please visit the test database:

Protection of personal information - Laboratory Medicine comply with the Trust Data Protection policy and have procedures in place to allow the Directorate and its employees to comply with the Data Protection act  1998 and associated best practice and guidance.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235