In reply to Dr Koch's comment below
> I admit to being curious about how Dr. Weinkove can be certain he has not
> seen any false negatives.
My original comment was as follows:
"We do not claim that normal results exclude a phaeochromocytoma,
however we have not found any false negative results."
No-one can be certain that they have not missed any false negatives.
But we still have not *seen* (or know of) any missed phaeos using
our individual metanephrine assay.We rely on feedback from those who
send us samples both from within the region (we provide a regional
service) as well as receiving many specimens from outside
laboratories. In the UK colleagues will not be embarrassed to tell us
when we are wrong! We do know of false negatives when we relied
solely on the urine catecholamine assays but so far this has not
happened with the metadrenaline and normetadrenaline assay.
Using a broader reference range from a
> population of hypertensives (even some who are receiving treatment) is
> appropriate, but at some point you gain specificity at the expense of
> clinical sensitivity, especially if you are testing a patient with new
> hypertension who hasn't received much, if any, treatment. The laboratory
> medicine of this disorder is complex, however, showing the delicate balance
> between economic pressures and physician trust as well as any set of
> analytes.
We know of patients where the diagnosis of phaeochromocytoma has been
missed in the UK. These cases arise when *no* test has been done by
the investigating clinician. Missed cases have *not* been due to
borderline urine results.
The main problem is not that of sensitivity but of getting the sample
in the first place. If multiple samples are requested, or dietary or
drug restrictions imposed, or tedious and dangerous collection
procedures demanded - the clinician is less likely to look for rare
diseases. In response to this reality we now plan to introduce a
simple overnight untimed urine collection procedure, using vitamin
C as the antioxidant in place of the potentially hazardous acid
currently used. Our preliminary findings were reported at the ACB
Focus 99 meeting held in Manchester in May this year [Al-Maney, Reed
and Weinkove: Ascorbic acid as a novel preservative for urinary
catecholamines and metadrenalines]
Cyril Weinkove
From: Dr Cyril Weinkove Tel: +44 (161)-787-4427
Clinical Sciences Building Fax: +44 (161)-787-4427
Hope Hospital, Salford Email: [log in to unmask]
M6 8HD, United Kingdom Internet:[log in to unmask]
Home Message and Fax Mail: +44 (171)-681-2373
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