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Table 4 Suggested kidney biopsy indications in connective tissue diseases

From: Renal involvement in autoimmune connective tissue diseases

Biopsy indication rapid deterioration of renal function (exclude post renal and pre renal disorders first)
Biopsy indication proteinuria >1 g/d (measured by collecting urine; collection over the course of a 24-hour period; to begin urine collection, the patient voids and discards the urine already in the bladder, afterwards urine for the next 24 hours has to be collected to ensure accurate results), if other causes of proteinuria are ruled out
the EULAR/ERA-EDTA recommendations for the management of lupus nephritis suggest performing a renal biopsy if reproducible proteinuria >0.5 g/d is present (especially with glomerular hematuria and/or cellular cases) [72]
Biopsy indication nephritic urine sediment (red blood cell casts) with deterioration of kidney function (estimated GFR <60 ml/min) if pre-existing impaired renal function is ruled out
Consider re-biopsy increase in proteinuria/serum creatinine despite ongoing immunosuppressive therapy (exclude post-renal and pre-renal disorders first); consider a repeat kidney biopsy due to potential phenotype change (for example, lupus nephritis)
Biopsy indication suspected interstitial nephritis, findings of white blood cell casts; leukocyturia (due to proton pump inhibitors, non-steroidal anti-rheumatic drugs, Sjögren syndrome, rheumatoid arthritis, and so on)
Biopsy indication diagnostic approach in case of uncertainties, when kidney involvement is suspected, but absolute indications are not met
  1. Renal biopsy suggestions differ between centers due to local preferences. General recommendations are difficult to define and we would consider higher levels of proteinuria (>1 g/d) compared to the EULAR/ERA-EDTA recommendations as biopsy indication for patients with lupus nephritis in our center.