Table 2.

Disease-specific workup for the most common indications

Disease	Specific laboratory tests	Diagnostic imaging	Special diagnostic tests
Acute inflammatory demyelinating polyradiculoneuropathy (Guillain–Barré syndrome)	Serum IgG antibodies to GQ1b	Spinal MRI	Lumbar puncture (elevated CSF protein) Electrodiagnostic studies (i.e., EMG and nerve conduction studies)
Anti-glomerular basement membrane disease (Goodpasture syndrome)	Urine analysis (hematuria, proteinuria, cellular casts) Renal function (creatinine) Anti-GBM antibodies (serum, kidney) ANCAs (MPO, PR3)	Chest CT	Kidney biopsy
Hyper-viscosity syndrome (in hyper-gammaglobulinemia, especially Waldenström macroglobulinemia)	M component quantification Viscosity measurement	Eye fundus examination
Catastrophic antiphospholipid syndrome	Lupus anticoagulant IgG and IgM anticardiolipin antibodies by ELISA Anti-beta2-GP I antibodies; IgG and IgM by ELISA Testing for DIC, HIT II, TMA	CT to rule out malignancy
Myasthenia gravis	Acetylcholine receptor antibodies Receptor-associated protein, MuSK-Ab Low-density LRP4 antibodies	CT or MRI of the mediastinum	Repetitive nerve stimulation test
N-methyl-D-aspartate receptor antibody encephalitis	Antibodies in serum and CSF (IgG antibodies to GluN1)	MRI	CSF EEG Rule out malignancy
Thrombotic thrombocytopenic purpura	Blood smear ADAMTS13 activity and inhibitor Hemolytic parameters Stool tests (cultures and Shiga toxin) Troponins	CT and MRI	ECG Echocardiography
Thyroid storm	TSH, T4, and T3 Thyrotropin receptor antibodies	Echocardiography Thyroid ultrasound	ECG
Acute liver failure	Liver enzymes Coagulation profile (including prothrombin time, INR and fibrinogen and TEG or equivalent, consider ADAMTS13 if pregnancy related and concern re TTP/aHUS) Complete blood counts and renal biochemistry Urine toxicology screen and serum paracetamol level Viral hepatitis screen + viral PCR if clinically pertinent (CMV, HSV, EBV) Pregnancy test Autoimmune markers Caeruloplasmin level Arterial ammonia Arterial blood gas and lactate Ferritin, triglycerides if HLH considered as a cause of ALF	Abdominal Doppler ultrasonography Alternative: abdominal CT	Liver biopsy (e.g., malignancy) Echocardiography (hepato-pulmonary syndrome)
ANCA-associated vasculitis/anti-GBM disease	ANCAs (MPO, PR3) Anti-GBM antibodies Antinuclear antibodies C3 and C4 Cryoglobulins Urinary sediment Tuberculosis screen	CT (head, orbits, mastoids, neck, thorax)	Biopsy of an affected organ BAL

MRI magnetic resonance imaging, CSF cerebrospinal fluid, EMG electromyogram, ANCA antineutrophil cytoplasmic antibody, MPO myeloperoxidase, GBM glomerular basement membrane, CT computed tomography, DIC disseminated intravascular coagulation, HIT heparin-induced thrombocytopenia, TMA thrombotic microangiopathy, ELISA enzyme-linked immunosorbent assay, MuSK-Ab antibodies to muscle-specific kinase, EEG electroencephalogram, TSH thyroid-stimulating hormone, T4 thyroxine, T3 triiodothyronine, ECG electrocardiogram, BAL bronchoalveolar lavage, INR International Normalized Ratio, PR3 proteinase 3, ALF acute liver failure, HLH hemophagocytic lymphohistiocytosis, TTP thrombotic thrombocytopenic purpura, TEG thromboelastography, aHUS atypical hemolytic uremic syndrome