ESR > 100 mm/hr

ESR – Test Principles 🌡️

• ESR = Erythrocyte Sedimentation Rate: as the name suggests, the ESR measures the rate at which RBCs settle in a vertical tube over one hour (mm/hr)

• RBC Repulsion vs. Attraction: normally, ⊖’tively charged RBCs repel each other. The addition of ⊕’tively charged proteins – namely, fibrinogen (acute phase reactant) & immunoglobulins (polyclonal response to infection vs. chronic inflammatory states) – results in electroneutralization allowing rouleaux formation, & RBC crosslinking respectively, both resulting in ↑ sedimentation due to ↑ mass/density

• Implication & Limitations: the observation of ↑ ESR generally implies the presence of inflammation, but completely lacks both sensitivity & specificity at low-level increases. On the other hand, rates > 100 mm/hr will usually have an apparent cause or undiagnosed illness requiring an explanation (normal, men = 0-15 mm/hr; normal, women = 0-20 mm/hr)

Extreme ESR – Epidemiology 🌎

• Infection: the most common cause in several series, with frequencies spanning from 33-44% of patients (nearly half!)

• Malignancy: a major runner up in several series, with frequencies spanning 12-58% of patients (metastatic in all cases)

• Renal Failure: another major runner up, accounting for up to 17% of patients

1st Pass = Most Common (Acute-Subacute)

2nd Pass = Least Common (Subacute-Chronic)

• The Blood Project – ESR

• Clinical Utility of the Erythrocyte Sedimentation Rate (AFP)

• Clinical Significance of Extreme Elevation of the Erythrocyte Sedimentation Rate (JAMA)