Isn’t there always going to be a better correlation in spiking experiments than in those which measure candidate analyte(s), because of the other unmeasured species which contribute to the effect?
Jonathan
On 3 Sep 2015, at 12:48, Hart, Tanya <[log in to unmask]> wrote:
> No correlation is quoted. Roche state that:
>
> "The L-index correlates with turbidity but not with triglyceride level"
> "Lipaemia is defined as turbidity in serum...the most frequent cause of lipaemia is an elevated triglyceride concentration"
>
> Not sure I agree with their definition of lipaemia - I think they are referring to elevations of the L-index. I suppose interpretation of the L-index depends on whether it's being used as a marker of triglyceride level or a marker of spectrophotometric interference.
>
> Tanya
>
> ________________________________________
> From: Clinical biochemistry discussion list [[log in to unmask]] on behalf of Daniel Smith [[log in to unmask]]
> Sent: 03 September 2015 08:08
> To: [log in to unmask]
> Subject: Re: Lipaemia index
>
> Hi Tanya,
>
> What is the quoted correlation from the manufacturer for lipaemia index and triglyceride concentration on the method sheet/insert?
>
> Danny
>
>> On 2 Sep 2015, at 16:34, Hart, Tanya <[log in to unmask]> wrote:
>>
>> We also use Roche Cobas (8000 & 6000), but the results unfortunately aren't so tidy when it comes to patient samples (attached).
>>
>> Tanya
>>
>>
>> Dr Tanya Hart
>> Clinical Scientist
>> Department of Clinical Biochemistry
>> Poole and Royal Bournemouth Hospitals
>>
>>
>>
>> -----Original Message-----
>> From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Paul Hamilton
>> Sent: 02 September 2015 15:54
>> To: [log in to unmask]
>> Subject: Re: Lipaemia index
>>
>> Dear All,
>>
>> I found a strong correlation between lipaemic index and triglyceride concentration measured on a Roche COBAS 8000 analyser, in a very small experiment using samples spiked with 20% intralipid. See attached chart.
>>
>> Best wishes,
>>
>> Paul
>>
>> Specialty Registrar in Chemical Pathology (Metabolic Medicine) Belfast Health and Social Care Trust Department of Clinical Biochemistry, Kelvin Building, Royal Victoria Hospital Grosvenor Road, Belfast, Northern Ireland, BT12 6BA
>>
>>
>>
>>
>> --------------------------------------------
>> On Wed, 2/9/15, Waller, Paul <[log in to unmask]> wrote:
>>
>> Subject: Re: Lipaemia index
>> To: [log in to unmask]
>> Date: Wednesday, 2 September, 2015, 15:34
>>
>> To add my own unpublished
>> observations;
>>
>> Intralipid
>> behaves very differently to endogenous chylomicrons, and can cause apparent interference in kinetic assays. My unproven hypothesis was that this was due to detergents/surfactants in reagents breaking down the lipid vesicles and thus causing a decrease in absorbance due to turbidity.
>>
>> I did not see this phenomenon
>> to the same extent in lipaemic patients sera.
>>
>>
>> Paul Waller
>> MSc CSci FIBMS FHEA
>> Associate Professor in
>> Biomedical Science
>> Associate Head
>> Biomolecular Sciences
>> School of Life
>> Sciences, Pharmacy and Chemistry
>> T 020 8417
>> 7783 (Direct Dial) / 67783 (Internal)
>> E [log in to unmask]
>> / Web page Mr Paul Waller
>>
>> Room PR MB 1019, Penrhyn Road, Kingston upon Thames, KT1 2EE
>>
>> Office
>> hours by appointment
>>
>> -----Original Message-----
>> From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
>> On Behalf Of [log in to unmask]
>> Sent: 02 September 2015 15:24
>> To: [log in to unmask]
>> Subject: Re: Lipaemia index
>>
>> Well put, Graham. I was going to reply
>> similarly, but I think you describe very well the variability in chylomicron particle size and their triglyceride content. As I mentioned previously in this thread, several publications and my own unpublished observations show that there is very little correlation between L (or T)-index and triglyceride concentration in lipemic specimens.
>>
>> Note
>> that Soha Zouwail mentioned to me off list that she found good correlation between the triglyceride concentration in Intralipid and L-index. I have used Intralipid to check for lipemia (turbidity) interference, but did not look at the correlation with the L-index. In fact, I think the last time I did such interference studies was before the specimen indices era. I think this makes sense though because the lipid vesicles of Intralipid are likely to be much more uniform than chylomicrons.
>>
>> -Jim
>>
>> -----Original Message-----
>> From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
>> On Behalf Of Graham Jones
>> Sent: Wednesday,
>> September 02, 2015 8:27 AM
>> To: [log in to unmask]
>> Subject: Re: Lipaemia index
>>
>> Derreck,
>>
>> I
>> expect not. Rather than having a lot of nice fresh chylomicrons, all the same size and same triglycerides (TG) content (and perhaps the same light scattering), I would expect in any sample we may have a range of difference sizes and TG content (and light scattering) as they lose TG to tissues on their way to the liver. Thus the relationship between TG and light scattering is not very close.
>>
>> Just my thoughts,
>>
>> Graham
>> ________________________________________
>> From: Clinical biochemistry discussion list <[log in to unmask]>
>> on behalf of Mccullough Derreck (UHMB) <[log in to unmask]>
>> Sent: Wednesday, 2 September 2015 6:45 PM
>> To: [log in to unmask]
>> Subject: Re: Lipaemia index
>>
>> Hi Jim,
>> As chylomicrons are
>> 90% triglyceride would you not expect a good correlation between triglycerides and turbidity if turbidity is caused by chylomicrons?
>>
>> Bw,
>> Derreck
>>
>> -----Original Message-----
>> From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
>> On Behalf Of [log in to unmask]
>> Sent: 26 August 2015 18:14
>> To:
>> [log in to unmask]
>> Subject: Re: Lipaemia index
>>
>> Replying to myself here! I agree with Alan that Sonia's triglyceride vs L- (or T-index) is much higher than expected. I've had a chance to dig out one of my
>> correlations: Triglyceride, mg/dL = 0.88 L-index + 185, R^2 = 0.017. (Sorry for U.S. units, but the key here is the very low R^2.) My bad that I didn't indicate the instrument/method on the graph, but it was a Roche instrument, probably an Integra. Also, earlier I implied that VLDL, being triglyceride rich, would increase the L/T-index. VLDL rarely does, but most often it is chylomicrons that cause the turbidity.
>>
>> Sonia, you mention that your L-index results are binned, that is, 1+, 2+, etc. yet your graph has numbers for the L-index. Does your Architect give you both the numerical L-index and the binned result?
>>
>> -Jim
>>
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>> <Trig vs L 0-20.jpg>
>> <Trig vs L all.jpg>
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