Steven Frost equired about indice for detecting haemolysis,lipaemia and
turbidity.
We have used these for many years with very satisfactory results. The
indices as set up initially on Hitachi analysers by Boeringher-Mannheim
(now Roche) provide quantitative detection of (oxy)haemoglobin, bilirubin
and lipaemia. They are set up in a way that limits cross-interference of
one substance with another. They work well "out of the box" but fine tuning
with your own instrumnt the coefficients may improve this aspect slghtly.
In general the results for the icterus index correspond well with bilirubin
results and haemolysis with haemoglobin measured by other methods. The
correlation of the lipaemia index with amounts of triglycerides is poor,
especially at relatively low concentrations (eg TG<10 mmol/L) and this is
indicated by Roche in their literature.
How do they compare with visual methods? In my opinion visual methods
should be consigned to the dust-bin of history whenever possible. The
indices can be performed on every sample and give (almost) the same
response at any time of day with any operator. The indices do not get tired
or forget to look. All samples can be checked which is not always true with
small sample tubes with a patient labelled wrapped right around. The
methods are stable and allow quantitative determination of cuttoffs at
which results may not be released.
My guess is that the terminology "serum indices" is to avoid the
implication that therse methods are actually measurements for thes analytes
inn question. This avoids FDA clearance etc as they are not reportable
results.
The Roche indices are the ones I am most familar with but simnilar ones or
semi-quantitative ones are available on many other analysers. For example
we have set up the H and I indices on an Olympus AU2700 and previously set
them on a scanning spectrophotometer for off-line checking of samples. The
important comparision is not between instruments but with the limits you
set in your own laboratory.
We use data generated in our own laboratory to determine what amount of
interference is too much and then withhold thos results with a footnote
indicating the reason. I find setting these limits is not a trivial matter
as the persuit of excellent results (minimal deviation due to an
interferent) has the cost of delays and client (Dr and Ptn) dissatisfaction
due to recollections.
Best wishes,
Graham
Graham Jones
Staff Specialist in Chemical Pathology
St Vincent's Hospital, Sydney
Victoria St, Darlinghurst, 2010
NSW, Australia
Ph: (02) 8382-2170 Fax (02) 8382-2489
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