Are we looking for Monoclonal Gammopathy of Renal Significance ( MGRS )? An audit of investigations in current clinical practice

ABSTRACT

Monoclonal gammopathy of unknown significance (MGUS) is a premalignant condition defined as the presence of a monoclonal protein with no evidence of plasma cell/B-cell-related malignancy. The risk of progression from MGUS to a related malignancy is approximately 1% per year. MGUS patients are closely monitored for signs of progression allowing for rapid initiation of treatment. In 2012, the International Kidney and Monoclonal Gammopathy Research Group (IKMG) introduced the term Monoclonal Gammopathy of Renal Significance (MGRS). MGRS is the clonal proliferation of a nephrotoxic monoclonal protein without meeting the criteria for any other plasma cell/B-cell malignancy. The diagnosis of MGRS allows for the initiation of urgent treatment required to prevent further deterioration in renal function. Updated diagnostic criteria from the IKMG made renal biopsy essential for diagnosis of MGRS. Consequently, the IKMG set out an algorithm to guide clinicians on when to consider a renal biopsy. The parameters measured to evaluate the need for a renal biopsy include urine albumin creatinine ratio (ACR). This audit was conducted in the Clatterbridge Cancer Centre Liverpool (CCC-L) a leading cancer centre in the Northwest of England. Urine ACR was chosen as the parameter to audit as it is a cheap, non-invasive, quantitative investigation. The primary outcome of this audit is to assess the number of MGUS patients who had an ACR measured at diagnosis in the Myeloma clinic from January 2014 to December 2020. Data were collected retrospectively from electronic clinic letters and notes. The date of diagnosis was defined as the date of clinic letter in which diagnosis was first confirmed. Patients were considered to have had an ACR performed at diagnosis if ACR was measured between 28 days prior to and post the date of diagnosis. ACR performed during disease was defined as any ACR measured from 28 days prior to date of diagnosis and date of death/data collection. Data from 503 patients (249 females, 254 males) were analysed. The median age at diagnosis was 73. Table 1 shows data for patients who had an ACR measurement performed at diagnosis and during disease. There is a trend towards greater compliance to measuring ACR at diagnosis in successive years from 2014 to 2019 (Table 1). This trend reverses in 2020 when only 40.0% of patients had an ACR measured at diagnosis. For all patients where ACR was performed during disease;56.8% ( n = 179) had the highest ACR measurement of <3.0 mg/mmol with only 14.0% ( n = 44) having the highest ACR measurement of >30.0 mg/mmol. If ACR was performed at diagnosis it was more commonly repeated if the value was higher;the frequencies with which ACR was repeated were 85.7% ( n = 12), 65.1% ( n = 28) and 28.4% ( n = 31) when ACR value at diagnosis was >30.0 mg/mmol, 3.0-30.0 mg/mmol and <3.0 mg/mmol respectively. This audit has shown an increased recognition for the importance of ACR measurement with increased compliance year on year. A likely hypothesis for the reduced measurements in 2020 is the need for remote clinic appointments during the Coronavirus 2019 (Covid-19) pandemic. Following IKMG guidelines 14.0% ( n = 44) of patients would be advised to have a renal biopsy due to their ACR measurement of >30.0 mg/ mmol. Further evaluation of this patient cohort is required to audit compliance with other parameters suggested by the IKMG. A diagnostic pathway to be used at the earliest opportunity for MGUS patients may then be developed..