Table 1.

Pathology definitions for scoring

LCCN: Histological diagnosis of LCCN was defined as follows: (1) at least one cast with typical appearance of LC cast by light microscopy; and (2) at least one cast staining for anti-κ or anti-λ conjugate by immunofluorescence or immunohistochemistry

LC cast: Tubular cast that meets ≥2 of these 3 criteria: (1) periodic acid–Schiff negative and/or polychromatophilic on trichrome and/or eosinophilic on hematoxylin-eosin and/or Congo red positive; (2) fractured and/or sharp edged and/or brittle and/or crystalline appearance; or (3) cellular and/or giant cell reaction around the cast

Glomerular definitions*

THP in the Bowman’s space: Identification of THP in the Bowman’s space

Tubulointerstitial definitions*

Tubular atrophy and interstitial fibrosis: Thickened tubular basement membranes, flattened epithelial cells, expanded interstitium with fibrosis in the cortex. <10% (0), 10%-24% (1), 25%-50% (2), >50% (3)

Interstitial inflammation: Increased interstitial leukocytes in the cortex. None (0), focal <50% of the cortex (1), diffuse ≥50% (2) assessed for the cortex, and separately for the medulla

Acute tubular injury: Cortical tubular epithelial flattening and loss of brush border, or necrosis of tubular epithelial cells, denudation of the tubular basement membranes

Interstitial edema: Expansion of the interstitium by edema

Tubulitis: Infiltrating mononuclear cells in the tubular epithelium of nonatrophic and atrophic tubule

THP extravasation: Identification of THP extravasation into the interstitium

Giant cell reaction around casts: Identification of at least one multinucleated histiocyte surrounding an LC cast

Tubular rupture: Interruption in the tubular basement membrane secondary to dilatation, to the presence of an LC cast or inflammation

Interstitial giant cell reaction: Identification of a least one multinucleated histiocyte in the interstitium

Extent of cast formation definitions assessed for the cortex, and separately for the medulla†

Estimated area (square millimeter): Total number of 20× fields of cortex/medulla multiplied by the area of one 20× field in square millimeter

Mean number of casts per square millimeter: Total number of casts in the cortex/medulla divided by the estimated area of cortex/medulla

Highest number of casts per square millimeter: Highest number of LC casts in one 20× field divided by the area of one 20× field in square millimeter

Vascular definitions*

Arteriosclerosis: Thickening of the intima with fibrosis or duplication of the elastic lamina. Absent (0), vascular narrowing of <25% of luminal area (1), 25%-50% of luminal area (2), >50% of luminal area (3)

Arteriolar hyalinosis: Accumulation of hyaline material in the arteriolar wall. Absent (0), mild (1), moderate (2), severe (3)

^*Evaluation based on all available slides.

^†Evaluation based on the most representative periodic acid–Schiff or trichrome-stained slide.