Dear Ed

Just out of interest, I did a count of the projected Cystatin workload

Our population is 375,000

Last financial year we did 34,853 microalbumin/ creatinine ratios for primary care

12,316 had a ratio of <3.0 and a GFR of 45-59 which put them in the NICE  Cystatin group G3A1

Ballpark figure for Cystatin C running on Roche Modular £16

So that’s £16*12316 = £197056

Ouch !!!, not so nice

BW John

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Dear Mailbase

The NICE updated guideline on CKD was published last week and there have been several responses posted. I am pleased the guideline has generated some debate and it is inevitable that new recommendations will take some working through. As a member of the NICE CKD guideline development group, I would like address some of these points:

1.            The recommendation “Consider using eGFRcystatinC for people with CKD G3aA1” is to improve risk stratification and provide reassurances to individuals at very low risk (i.e. those who are G3aA1 [GFRcreatinine 45-59 with no albuminuria] and whose eGFRcystatin is found to be >=60. (See e.g. Peralta CA, et al. Detection of chronic kidney disease with creatinine, cystatin C, and urine albumin-to-creatinine ratio and association with progression to end-stage renal disease and mortality. JAMA 2011;305(15):1545-52. Shlipak MG, et al. Cystatin C versus creatinine in determining risk based on kidney function. N Engl J Med 2013;369(10):932-43. Waheed S, et al. Combined association of albuminuria and cystatin C-based estimated GFR with mortality, coronary heart disease, and heart failure outcomes: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Kidney Dis 2012;60(2):207-16. Foster MC, et al. Novel filtration markers as predictors of all-cause and cardiovascular mortality in US adults. Am J Kidney Dis 2013;62(1):42-51.) It is not primarily included as a measure to improve accuracy of GFR estimation (see e.g. arguments in Rule AD, Glassock RJ. GFR estimating equations: getting closer to the truth? Clin J Am Soc Nephrol 2013;8(8):1414-20).

2.            The GDG would not have considered the recently published CAPA GFR equation (Grubb et al, Clinical Chemistry 2014) as this was outwith the search time window used during guideline development. However, as stated above the suggested use of cystatin C is around risk evaluation and the evidence for risk stratification using the CAPA cystatin C equation does not presently exist to my knowledge.

3.            Regarding standardisation [“…significant issues with standardization of cystatin C assays (which I am sure bypassed NICE completely!)]”: the guideline recommends the use of a cystatin C assay calibrated to the international standard. Of course differences exist between methods, although the Grubb et al paper actually shows quite good agreement between most commercial assays. It is our job as laboratory professionals to ensure we use appropriately standardised assays and, through quality assurance, to ensure ongoing maintenance and traceability of the data we produce.

4.            The uncertainty issue (“…ability to distinguish GFR 44 or 45 etc”) is no different to many other diagnostic threshold arguments in laboratory medicine. I note Dr Bosomworth’s sensible comments in this regard (posted 30th July) and re-iterate that a CKD diagnosis should never be based upon a single test result.

5.            It is an obvious truth that GFR estimating equations make assumptions about the relationship between age, gender and muscle mass (“…bird like old ladies with extremely low BMI’s and muscle mass…etc”). But the alternative – use of a serum creatinine reference range against which data should be interpreted – is in my opinion more flawed.

6.            The benefits of routine use of estimated GFR (“Is there any evidence yet of improved outcomes from routine reporting of eGFR?”) have been discussed (e.g. see review Levin A, Stevens PE. Early detection of CKD: the benefits, limitations and effects on prognosis. Nat Rev Nephrol 2011;7(8):446-57.)

Is there any evidence yet of improved outcomes from routine reporting of eGFR? I repeatedly asked the ACB for this after their statement but I haven't seen any.

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------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content. ACB Web Site http://www.acb.org.uk Green Laboratories Work http://www.laboratorymedicine.nhs.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/