urine, cerebrospinal fluid (the fluid surrounding the spinal cord and brain), faeces,
sweat, saliva and amniotic fluid. It is essential that the samples are collected in the appro-
priate container at the correct time (particularly important if the test is for the measure-
ment of hormones such as cortisol subject to diurnal release) and labelled with
appropriate patient and biohazard details. Samples submitted to the laboratory for
biochemical tests are accompanied by a request form, signed by the requesting clinician,
which gives details of the tests required and brief details of the reasons for the request to
aid data interpretation and to help identify other appropriate tests.Laboratory reception
On receipt in the laboratory both the sample and the request form will be assigned an
acquisition number usually in an optically readable form but with a bar code. A check is
made of the validity of the sample details on both the request form and sample container to
ensure that the correct container for the tests required has been used. Samples may be
rejected at this stage if details are not in accordance with the set protocol. Correct samples
are then split from the request form and prepared for analysis typically by centrifugation
to prepare serum or plasma. The request form is processed into the computer system that
identifies the patient against the sample acquisition number, and the tests requested by the
clinician typed into the database. It is vital at this reception phase that the sample and
patient data match and that the correct details are placed in the database. These details
must be adequate to uniquely identify the patient bearing in mind the number of potential
patients in the catchment area, and will include name, address, date of birth, CHI number
(a unique identifier for each individual in the UKfor health purposes), hospital or Accident
and Emergency number and acquisition number.16.2.2 Analytical organisation
The analytical organisation of the majority of clinical biochemical laboratories is
based on three work areas:- auto-analyser section,
- immunoassay section,
- manual section.
Auto-analyser section
Auto-analysers dedicated to clinical biochemical analysis are available from many
commercial manufacturers. The majority of analysers are fully automated and
have carousels for holding the test samples in racks each carrying up to 15 samples,
one or two carousels each for up to 60 different reagents that are identified by a
unique bar code, carousels for sample washing/preparation and a reaction carousel
containing up to 200 cuvettes for initiating and monitoring individual test reactions.
The Abbott ARCHITECT c1600 (Fig. 16.1) utilises three methodologies: spectropho-
tometry, immunoturbidometry and potentiometry. The spectrophotometry system is
capable of measuring at 16 wavelengths simultaneously whilst the potentiometric
system, based on the use of ion-selective electrodes (ISEs) (Section 1.3.5) that are632 Principles of clinical biochemistry