716 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 23.5: Serum proteins in different clinical conditions

 

Classification of Analyzers

There are several types of analyzers available in the market.

They may be grouped in two categories:

¾ Semiautomated analyzers

¾ Automated analyzers

Semiautomated Analyzers

Instruments with an absorbance linearity of 2.0 are suitable

for turbidimetric estimations of both particle enhanced

and non-particle enhanced reagent systems. Most of the

instruments with the above specification can be used for

turbidimetric measurements using the absorbance mode.

In the absorbance mode as the calibration curve cannot be

stored, it has to be drawn manually.

Among the instruments working on cuvette mode

for measuring absorbance, very few instruments have

software interface programmed with a facility to store the

calibration curve utilizing both the principles of reading,

i.e. ‘real sample blanking’ and ‘immediate mixed blanking’

in the multistandard mode. Many instruments with cuvette

modes are known to have programes in multistandard

mode to store calibration curve for assay systems using the

real sample blanking techniques only.

Automated Analyzers

The automated analyzers can be grouped in two categories:

¾ Centrifugal analyzers

¾ Static instruments (non-centrifugal analyzers).

Centrifugal Analyzers

In these analyzers, the cuvettes are arranged in circle

(rotor) that can be rotated at a velocity of about 1000

rpm. The shape of each cuvette allows application of

sample and reagent (reaction buffer, antibody) in separate

compartments. When the rotor starts to spin, the contents

of these compartments are mixed simultaneously and

held in place in the cuvette by centrifugal force. Readings

of all the cuvettes are performed at essentially the same

time (i.e. when the rotating cuvettes are passing the optical

measuring device). Two reading systems are used: either

parallel to the length of the cuvette where the volume in the

cuvette is proportional to the light path or perpendicular

to the length of the cuvette where the width of the cuvette

equals the light path.

Static Instruments

In these instruments, the cuvettes are mostly arranged in

a circle (rotor), and this is slowly rotated in step at a fixed

time interval (cycle time). Access to the cuvette is possible

only at these intervals for sample or reagent application

and reading. Mixing is in most cases performed with a

mechanical stirring device. Modern instruments seem

more and more to be based on these principles.

All instruments operate under software control. A

part of this software is the user interface that makes it

possible to program the instrument to perform analysis

and calculation according to an optimized protocol. The

analytical parameters available for user control vary from

instrument to instrument.

Some instruments, however, are “closed instruments”

which implies that all parameter settings are read into the

instruments by bar coded reagents. In this case, the user

cannot control the assay and will have to rely entirely on

the manufacturer and their instructions.

The applications and reference values of important

clinical analytes are shown in Table 23.4.

Given below are serum proteins with clinical conditions

where they are raised and diminished (Table 23.5)

Diagnostic Immunology 715

TABLE 23.4: Applications, reference values of important clinical analytes

Analyte Description Reference values Applications

RF Quantitation of

rheumatoid factors

< 10 lU/mL Detection of RA, differential diagnosis of RA from rheumatic fever and

other rheumatic disorders

CRP Quantitation of C-reactive

protein

Adults and children

< 0.6 mg/dL

Detection of inflammatory conditions, measuring the severity of

conditions, differential diagnosis of bacterial and viral infections

Monitoring the response to therapy

CRP US Quantitation of

ultrasensitive levels of

C-reactive protein

< 0.05 mg/dL Prognostic cardiac marker

ASO Quantitation of

antistreptolysin ‘O’

Children : < 150 lU/mL

Adults : < 200 lU/mL

Detection of Group A streptococcal infections such as sore throat,

rheumatic fever, rheumatic heart disease

MA Quantitation of urinary

albumin

< 20 mg/L Detection of microalbuminuria. Monitoring the effect of ACE inhibitor

or intervention strategies for reducing UAE*

IgA Quantitation of

immunoglobulin IgA

70–400 mg/dL Chronic infections of GI and respiratory tract, anaphylactic transfusion

reactions, monitoring progress of IgA myeloma

IgG Quantitation of

immunoglobulin IgG

700–1600 mg/dL IgG myeloma, IgG deficiency, assessment of the progression and

response to treatment of IgG myeloma

IgM Quantitation of

immunoglobulin IgM

40–230 mg/dL Monitoring patients with Waldenström’s macroglobulinemia

Estimating frequent, chronic and acute infections

IgD Quantitation of

immunoglobulin IgD

3–14 mg/dL Screening for congenital infections. Monitoring IgD myeloma

IgE Quantitation of

immunoglobulin IgE

Adult 3–423 lU/mL Assessment of atopic diseases, dermatologic and parasitic infections

C3 Quantitation of

complement component

C3

90–180 mg/dL C3 deficiency, recurrent infections detection and monitoring

of immune complex disorders such as SLE, vasculitis,

glomerulonephritis, autoimmune hemolytic anemia

C4 Quantitation of

complement component

C4

10–40 mg/dL Congenital deficiency in lupus erythromatosus

Hereditary angioneurotic edema

Recurrent infections

AT III Quantitation of

antithrombin II

17–30 mg/dL Evaluating patient at risk of developing thrombotic-embolic disease. In

surgical patients receiving heparin, assessment of thrombotic risk of

contraceptive or estrogen therapy

Apo A-1 Quantitation of

apolipoprotein A-1

Males: 105–175 mg/dL

Females: 105–205 mg/dL

lndependent risk factor for coronary artery disease

Apo B Quantitation of

apolipoprotein B

Males: 60–140 mg/dL

Females: 55–130 mg/dL

Elevated Apolipoprotein B levels are associated with atherosclerosis

Lp(a) Quantitation of

lipoprotein(a)

< 300 mg/L Risk factor for coronary heart disease that is independent of all other

lipid parameters

β2-M Quantitation of

β2-Microglobulin

< 60 years : 0.8–2.4 mg/L

> 60 years : < 3.0 mg/L

Prognosis of multiple myeloma

Early detection of renal transplant rejection, differentiation of

glomerular and tubular nephropathies,

Monitoring therapeutic response of patients with nonsecretory

myeloma or light chain disease

Cp Quantitation of

ceruloplasmin

20–60 mg/dL Diagnosis of Wilson’s disease,

Menkes disease, nutritional copper deficiency

Hp Quantitation of

haptoglobin

30–200 mg/dL Diagnosis and of monitoring of hemolytic diseases

*UAE = Urinary albumin excretion

Note: The above reference values are for guidance only. As the reference values are related to age, geographical and methodological

differences and vary widely. Each laboratory should define its own reference range for the relevant population.

716 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 23.5: Serum proteins in different clinical conditions

Protein Increased in Decreased in

Serum albumin Rare, usually associated with

hemoconcentration

Acute phase response, severe liver disease, nephrotic syndrome,

other renal diseases, malnutrition, pregnancy, premature infants

Complement

Complement C3 APR (infection, inflammation etc.), biliary

obstruction, obstructive jaundice, diabetes

mellitus, gout, some connective diseases

(excluding SLE)