Biomedical Engineering Reference
In-Depth Information
to take into account LC-MS/MS-specific requirements, which may not always be
easy to implement in the routine laboratory [ 1 ]. Only after equipment has been
successfully installed (possibly documented by an operation qualification; OQ) can
a laboratory start to prepare an assay (performance qualification; PQ). Once the limi-
tations of the assay are laid down, a subsequent validation and a risk analysis usually
conclude the months-long process of a LC-MS/MS platform establishment. It must
not be forgotten that a frequently observed considerable method bias towards immu-
nological or other methods might necessitate a parallel measurement phase of several
weeks or even months, to accustom the clients to the new measured value [ 2 ] .
2
Application Fields
In many industrialized countries FIA-MS/MS is now used in the routine neonatal
screening for inherited diseases of metabolism. Typically, these analyses are per-
formed by a few specialized laboratories per country and a specified set of metabo-
lites is traced in a semi-quantitative manner [ 3, 4 ]. Besides these applications, at
least one HPLC-MS/MS system is available in most university hospital laboratories
in industrialized countries (e.g. in clinical chemistry institutes, pharmacological and
forensic institutes, institutes of occupational health, mass spectrometric core facili-
ties). Here, they are often used for both research and routine analytical purposes,
serving application fields like therapeutic drug monitoring (TDM; in particular
quantification of immunosuppressants and new generation anticonvulsive and antip-
sychotic drugs), pharmacology, endocrinology, and toxicology. For more detailed
information, the readership is referred to the literature [ 5- 14 ] . Beyond university
hospital laboratory centres only few tertiary care hospitals in Europe are equipped
with a HPLC-MS/MS instrument at present. In addition, the majority of larger labo-
ratory trusts are nowadays equipped with HPLC-MS/MS instruments, mostly in
centralized core facilities. These instruments are predominantly used for TDM and
endocrinology. HPLC-MS/MS methods replace more and more of the numerous
conventional HPLC-UV and HPLC-FLD methods in such laboratories since they
offer superior specificity, shorter runtimes, and less laborious method development
and sample preparation.
Tandem mass spectrometer based protein quantification made tremendous tech-
nological advancements in the past years, transforming LC-MS/MS based proteom-
ics from a mere qualitative screening biomarker discovery tool to a quantitative
targeted biomarker verification oriented platform (“quantitative clinical proteom-
ics”) [ 15 ] useable in clinical practice [ 16, 17 ]. In this context—besides the specificity
of MS/MS detection—the possibility to monitor a bundle of biomarkers simultane-
ously, distinguishes LC-MS/MS platforms remarkably from immunoassay based
approaches [ 18- 20 ]. Valid and inter-laboratory transferable concepts of target pro-
tein enrichment followed by tryptic breakdown to peptides amendable to LC separa-
tion are now well established [ 21, 22 ]. Protein quantification is usually carried out
by assessing the MS/MS response of a set of carefully chosen reporter peptides by
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