There is a paper on this subject published in the December or november 
2001 issue in pregnant subjects using o-Dianisidine.
That paper concludes that pregnants have decreased oxidase activity
suggesting the depletion of Cu deposits so as to take of foetus's
requirements.
S.Vivek
Guy's St.Thomas' &
Barnet & Chase Farm


On Wed, 12 Dec 2001, [log in to unmask] wrote:

> I agree with Nick Miller's comments about the value of the PPD ferroxidase
> assay.  Are any UK labs offering this at present?  The Wilson's clinic at
> the Middlesex (John Walshe, Andrew Lees and myself) has been dependent on
> the paraphenylenediamine-Cp offered by Dr Herb Scheinberg at the National
> Wilson Disease Center in New York but his lab unfortunately had to close
> earlier this year.
> 
> I disagree with the formula for relating caeruloplasmin Cp and copper
> Cu, 'though (Nick's formula is presumably, (Cp mg/dl)5 = Cu ug/dl):
> 
> 0.3 % of Cp is Cu, by mass
> Non-Cp associated Cu should be ~10 ug/dL or ~1.57 µmol/L or ~10% total
> copper,
> so
> (Cp mg/dl)3 + 10 = Cu µg/dl
> i.e. Cu µg/dl - (Cp mg/dl)3 <= 10
> or
> (Cp mg/L)0.0472 + 1.574 = Cu µmol/L
> i.e. Cu µmol/L - (Cp mg/L)0.0472 <= 1.57
> 
> This formula holds for PPD-Cp but may give negative results for non-Cp
> associated copper where Cp is measured immunologically, presumably because
> apoCp bears the same epitope/s as those recognised by some antibodies to
> holoCp.  This may account for some of the differences encountered in
> Western Australia.  It certainly causes problems in the biochemical
> assessment and monitoring of patients with Wilson's disease when the only
> Cp assay available is immunological.   A goal for long-term chelation
> treatment is to ensure that non-Cp associated Cu remains consistently <10
> ug/dl or 1.57 umol/L.  However, treated WD patients may have appreciable
> circulating apoCp so may have (spuriously) negative non-Cp Cu using this
> formula.  ApoCp has no ferroxidase activity and negative formula results
> rarely occur using the PPD assay.
> 
> Godfrey Gillett
> 
> ----------
> From:  Nicholas Miller[SMTP:[log in to unmask]]
> Reply To:  Nicholas Miller
> Sent:  12 December 2001 11:57
> To:  [log in to unmask]
> Subject:  Re: Caeruloplasmin. Beckman v Dade Behring
> 
> Different antibodies, different results: in any case the important
> measurement is the ferroxidase activity of the protein, not its
> concentration in the serum. If you want to try and resolve the problem by
> adding another leg to your comparison,
> 
> a) you might consider doing ceruloplasmin by determining the oxidase
> activity (Ravin HA, J Lab Clin Med 1961, 58:161) which is the method given
> in the older editions of Varley. It's very simple and works well on Cobas-
> type equipment. If you look at the later edition of Varley (by which I mean
> the 1988, 6th edition) you'll find that the new authors make disparaging
> comments about this method, but my experience is that is more precise and
> reproducible than the immunometric methods, with a much better linearity
> range. I suspect they had got fed up with re-crystallising the para-
> phenylenediamine substrate (which is quite toxic and still not supplied in
> sufficient purity ). Another problem is that lyophilised sera have no
> enzymatic activity by this method, so you have to calibrate with a frozen
> serum pool.
> 
> b) measure serum copper and see which antibody gives the best agreement
> [serum copper (mg/dl) x 5  =  serum CPL (mg/dL), e.g. Serum Cu of 160 is
> equivalent to a CPL of 32].
> 
> 
> Nick Miller,
> 
> London
> 
> -----Original Message-----
> ----------
> From:  Musk, Sandy[SMTP:[log in to unmask]]
> Reply To:  Musk, Sandy
> Sent:  12 December 2001 05:17
> To:  [log in to unmask]
> Subject:  Caeruloplasmin. Beckman v Dade Behring
> 
> A small local survey on specific proteins was recently conducted in Western
> Australia.
> The results for caruloplasmin on fresh serum samples show that the results
> by the Beckman Immage were on average 33% higher than on the Dade Behring
> BNII.
> Subsequent investigation using lyophilised QC material only show about a 10%
> difference.
> It is my understanding that both are standardised against the IFCC
> International Protein Standard CRM 470.
> A similar survey conducted in 1996 with Beckman Array and BNA did not show
> this difference.
> 
> Has this difference been reported before?
> Any comments would be appreciated.
> 
> Mr Sandy Musk
> Senior Scientist in Charge
> Special Chemistry
> Core Clinical Pathology and Biochemistry
> Laboratory Services
> Royal Perth Hospital
> Western Australia
> Phone 08 9224 11
>