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🧪 Acetylcholine Receptor Antibodies (AChR-Ab) Test

Aspect	Details
Fasting Required?	❌ Not required
Sample Type	Blood (serum)
Main System Involved	Neuromuscular junction, immune system
Primary Use	To diagnose autoimmune myasthenia gravis (MG)

🧬 What Are AChR Antibodies?

Acetylcholine receptors (AChRs) are located at the neuromuscular junction, where nerve impulses stimulate muscle contraction.
In myasthenia gravis, the immune system mistakenly creates antibodies against these receptors, impairing the transmission of signals.
The AChR-Ab test detects these autoantibodies in the blood.

🧠 Clinical Importance

Use Case	Why It’s Done
✅ Diagnosis of Myasthenia Gravis	Confirms autoimmune basis of muscle weakness
🧪 Subtype classification	May differentiate between generalized vs ocular MG
📈 Monitoring disease activity	In select cases, may help assess response to treatment
🧬 Thymoma evaluation	MG patients may have thymic tumors that stimulate antibody production

🩺 Interpretation of Results

Result	Possible Meaning
Positive	Likely myasthenia gravis (85–90% in generalized MG, 40–70% in ocular MG)
Negative	MG still possible (especially ocular MG); may require MuSK or LRP4 antibody testing

🔬 Subtypes of AChR Antibodies (Sometimes Reported Separately)

Subtype	Function
Binding antibodies	Most common, interfere with receptor activation
Blocking antibodies	Prevent acetylcholine from binding
Modulating antibodies	Promote degradation of the receptor

Most commercial labs report total AChR antibodies (combining subtypes).

🧪 Associated & Follow-Up Tests

Test	Purpose
MuSK Antibodies	For AChR-negative MG patients
LRP4 Antibodies	In seronegative MG
EMG/Nerve Conduction Studies	Measures muscle fatigue and transmission
CT/MRI of chest	To look for thymoma
Tensilon (edrophonium) test	Historical test for rapid symptom improvement

🧠 Conditions AChR-Ab Test Helps Diagnose

Condition	Relation
✅ Myasthenia Gravis (MG)	Autoimmune attack on ACh receptors
🧬 Thymoma	AChR-Ab present in ~30–45% of thymoma cases
❌ Other autoimmune disorders	May occasionally be weakly positive in lupus or RA

✅ Summary Table

Test	Purpose	Sample	Positive In
Acetylcholine Receptor Antibody (AChR-Ab)	Diagnose myasthenia gravis	Blood	~85% of generalized MG

Acetyl Choline Receptor Antibodies (AChRab)