Sensitivity and Specificity of Pathologic Finding to Diagnose Lupus Nephritis.

Diagnosing lupus nephritis is easy – if the diagnosis of systemic lupus erythematous is provided with the clinical information! If not, things may become more difficult. The updated EULAR/ACR criteria of last year (1) allow the diagnosis of SLE with a sensitivity of 96.1 % and a specificity of 93.4 %. A class III or IV lupus nephritis in addition to antinuclear antibodies with a titer of ≥ 1:80 on at least one occasion will be enough to make the diagnosis if there is no better explanation for the glomerulonephritis. In contrast, a class II or V lupus nephritis will require additional criteria for the diagnosis of SLE. The paper by Kudose et al. (2) helps us to find arguments in favour of lupus nephritis. Although the authors do not provide the data on light microscopic glomerulonephritis patterns, it seems that light microscopy does not help. It is immunohistology (full house pattern, intense C1q staining, extraglomerular deposits) and electron microscopy (combined subendothelial and subepithelial deposits, tubuloreticular structures) that make the difference. Still, the features do not add up to 100 % specificity. Therefore, lupus nephritis will continue to require a careful clinico-pathologic correlation – in both easy and difficult cases.

(1) Arthritis Rheumatol. 2019; 71:1400-1412.
(2) Clin J Am Soc Nephrol 2019; 14:1605-1615.