Immunology, Autoantibodies & Complement

Calculate the age- and sex-adjusted upper limit of normal for the erythrocyte sedimentation rate using Miller’s formula, instead of applying a fixed cut-off of 20 mm/h.

Convert alpha-1 antitrypsin between mg/dL, g/L, mg/L and µmol/L, with the protective threshold and why an acute-phase rise can hide a deficient patient.

Convert doubling dilutions past 1:40 into a reciprocal ANA titre, and see when a change actually means something.

IU/mL and U/mL are the same number and IU/L is a thousand times larger — so the value of this page is the interpretation, not the arithmetic.

Convert beta-2 microglobulin between mg/L, µg/mL and nmol/L, with the ISS myeloma thresholds and why renal function dominates the interpretation.

Interpret anti-tTG IgA, total IgA and EMA together, and see why a gluten-free diet before testing invalidates the result.

Convert complement C3 between g/L, mg/dL and mg/L, and read it the way it should be read — as a pattern with C4, not as a number on its own.

Convert C-reactive protein between mg/L, mg/dL and µg/mL, and see why the tenfold difference between the two mass units is the trap that matters.

Calculate DAS28-CRP for rheumatoid arthritis disease activity, and see the joints and biases it does not capture.

Convert IgA between g/L, mg/dL and mg/L — and check it before you trust a coeliac screen, because IgA deficiency makes tissue transglutaminase IgA uninterpretable.

Convert IgG between g/L, mg/dL and mg/L, and see why a raised total cannot tell a polyclonal rise from a paraprotein.

Stage newly diagnosed multiple myeloma from beta-2 microglobulin and albumin, and see how R-ISS builds on it.

Calculate the kappa:lambda free light chain ratio, and see why the normal range shifts in renal impairment.

Convert total IgE between kU/L, IU/mL and ng/mL, and see why the number is a poor standalone allergy test.