EGFR Lower Limit

Is there a need for a lower reporting limit ??

Our understanding of the need for EGFR is to try and ensure a common approach is applied, particularly in the primary care setting, to monitoring renal function mainly in high risk groups such as diabetes, hypertensives and ischaemic heart disease patients. This allows a consistent approach to be observed with appropriate interventions with mild renal impairment in the primary care setting and opportunity to refer to secondary care when more aggressive approaches to therapy are needed    

The renal NSF indicates patients should be referred to secondary care at a renal unit when Stage 4/5 of CKD has been established

The EGF level at which this is indicated is Stage 4  EGFR = 15 to 29

Stage 5  EGFR = <15

In a 65 yr old man an EGFR of 29 (ie stage 4 CKD) reflects a creatinine of 200umol/L

In a 65yr old man an EGFR of 15 (ie stage 5 CKD) reflects a creatinine of 350 umol/L

This apparently modest numerical change in EGFR clearly represents a highly significant numerical change in creatinine level. 

We have a number of patients being monitored in primary care with creatinines above 200umol/L (and ostensibly at CKD grade 4) having EGFR calculated who are being monitored and cared for in primary care.

Our secondary care renal services do not request EGFR on any of our patients. One has to suppose that EGFR use when CKD has reached this level is inappropriate 

Can one therefore presume that the best mechanism of monitoring CKD  in patients from a primary care setting is that once a patient has reached the magical EGFR = 30 level that it would be more appropriate to report <29 and switch to monitoring via creatinine level?