Baseline characteristics of participants enrolled in FORM-2C, an observational study of primary care patients with reduced eGFR

Problem

The FORM-2C (Frequency Of Renal Monitoring – Cystatin C and Creatinine) Study is an observational study of primary care patients with reduced eGFR. Participants are recruited on the basis of a reduced eGFR measurement (<90ml/min/1.73m2) within the last 12 months, and are followed up for two years. The intention is to test the ability of eGFR as calculated using two different markers (creatinine and cystatin C) to predict deterioration in renal function. This abstract reports baseline characteristics and follow-up rates for the FORM-2C cohort.

Approach

We have successfully recruited 749 participants to FORM-2C, over a period of 24 months. Participants attend a baseline visit, followed by 6 follow-up visits. We also obtain separate consent for notes review to follow patients up for outcomes at 5 years. At each visit, patients provide blood and urine samples for measurement of various biochemical markers associated with kidney function.

Findings

Participants in FORM-2C have an average age of 69.9 years (SD 9.75). We have an even gender balance, with 385 (51.4%) of participants reported as female, although the ethnic mix is poor, with the vast majority of participants (699, 93.3%) identifying as White British. Most participants had records of pre-baseline eGFR (741 participants, 98.9%), with measurements being recorded a median of 119 days (IQR 49-195 days) before the baseline visit. Most participants had a baseline eGFR measurement recorded (658, 87.9%).The mean pre-baseline eGFR was 66.7 ml/min/1.73m2 (SD 13.5). The mean baseline eGFR was 66.5 (SD 14.5) ml/min/1.73m2. Although 23% of participants had discordant staging between baseline and pre-baseline eGFR, at least 82% had stage 2 or 3 CKD at baseline. CKD stage based on baseline eGFR was stage 2 in 416 (55.5%), 3a in 145 (19.4%) and 3b in 55 (7.3%). We are currently experiencing good follow-up rates, with over 85% follow-up at all visits. In addition, the discontinuation rate for the cohort is currently only 5.1%, with 135 (18%) of the cohort having successfully completed their final visit. Of those completing their final visit, 88% have consented to extended follow-up.

Consequences

We have successfully recruited a cohort of patients with early-stage CKD, and have shown that we are able to follow up these patients, and obtain high levels of consent for extended follow-up. We are confident that these will allow us to produce robust results from this study.The limited ethnic diversity of the FORM-2C cohort is disappointing, and may limit the applicability of the results of FORM-2C to more ethnically diverse populations. This is likely to be due to the ethnic mix in the Oxfordshire area, where recruitment took place, although this has allowed us to use a single laboratory and hence ensure low variability in our biochemistry results.