Background/Purpose: Renal biopsy is the gold standard for assessing renal activity and hence guiding treatment. Whether a repeat renal biopsy is helpful during flares of LN remains unclear. In the present study, we retrospectively reviewed LN patients who had more than one renal biopsy, in the hope of finding the clinical advantage of repeat biopsy

Methods:  The sample comprised 243 patients with systemic lupus erythematosus (SLE) treated between 1980 and 2013 at a tertiary university hospital that does not treat pediatric populations. The patients were registered in a specific database. From a total of 126 patients with LN, we selected those who underwent 2 renal biopsies for analysis. Renal biopsies were evaluated according to the WHO classification  or the ISN/RPS classification (in use since 2004).

Results: We identified 28 SLE patients with LN for whom it was possible to compare reference and repeat biopsies. In total, 56 renal biopsies were considered. Overall, in 14 patients (50%), paired biopsies showed changes in the pathological pattern. Table 1 shows the pathological classification on repeat biopsy:

Reference biopsy	Repeat biopsy
Class II Mesangial LN    N=9	1 switched to Class I 2 no shift in pathological class 6 switched to higher grade nephritis (Class IV: 3 cases, Class V: 3 cases).
Class III Focal LN N=4	2 no shift in pathological class 2 switched to higher grade nephritis (Class IV: 1 case, Class V: 1 case)
Class IV Diffuse LN N= 13	1 switched to Class II and 3 to Class III 9 no shift in pathological class
Class V Membranous LN N=2	1 switched to Class IV 1 no shift in pathological class

In the subgroup of patients with Class II mesangial LN, the repeat biopsy showed a transformation to a higher grade of nephritis (Class IV or V) in 67% of the cases.

In contrast, in most patients (65%) with proliferative classes (III and IV), there was no shift in histological class on repeat biopsy. Of the 2 patients with Class V membranous LN, only 1 changed to a proliferative class. Clinically significant class switches during LN flares were more frequent in patients with non-proliferative lesions (Classes II and V) than those with proliferative lesions (classes III and IV) in their reference biopsy (p<0.05).

The mean renal activity index on first biopsy was 8.85 (SD: 4.43) and on repeat biopsy it was 7.26 (SD: 3.84) (p = 0.315). The mean chronicity index for the first biopsy was 1.95 (SD: 2.53) and for the repeat biopsy it was 2.52 (SD: 2.39) (p<0.001).

The pathological transition could not be predicted by any clinical characteristics. After the repeat biopsy, 10 (36%) of patients had a change of treatment regimen: 8 received an increase in immunosuppression; while in 2 cases immunosuppressive therapy was decreased or stopped.

 Conclusion: Pathological conversion was highly prevalent (50%) in patients with LN. Overall, 66% of cases with class II mesangial LN in a reference biopsy showed transformation to a higher grade of nephritis (class IV or V) on repeat biopsy, so early repeat biopsy is advisable for this subgroup of patients. In contrast, in most patients (65%) with proliferative Classes (III and IV) in a reference biopsy, there was no shift in histological class on repeat biopsy.

Repeat biopsy might be helpful in guiding treatment, both to identify those patients for whom it is necessary to intensify immunosuppression therapy, and to avoid unnecessary increased immunosuppression therapy in others.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-clinical-relevance-of-a-repeat-biopsy-in-lupus-nephritis-ln-flares/