1. Interpolate ∆A of the diluted test specimen on the
calibration curve and obtain the RF concentration ‘C’
2. Multiply the RF concentration ‘C’ with the dilution
factor (F) of the test specimen for obtaining the
concentration of RF in the neat test specimen.
Concentration of RF in the neat test specimen in IU/mL
(where ‘F’ is the dilution factor of the test specimen, i.e.
10 for 1:10 dilution of test specimen and so on).
Specific Performance Characteristics
The QUANTIA-RF reagent has been designed to measure
RF concentrations in the range 7.5–120 IU/mL and is linear
Detection Limit/Analytical Sensitivity
The detection limit represents the lowest measurable
RF concentrations that can be distinguished from zero.
No prozone effect was observed up to a concentration of
No interference was observed with:
Interference factor No interference up to
The reference values of RF in normal population are <10
Each laboratory should define its own reference range
1. Usage of well-calibrated equipment and accessories
and procedures is critical for achieving correct
2. When ∆A obtained for the test specimen is greater
than the ∆A of the standard with highest concentration
then, it indicates that the concentration of IgA in the
test specimen is beyond the measuring range of the
QUANTIA-RF assay. Such specimens should be rerun
3. Markedly lipemic, hemolyzed, and contaminated
serum samples could produce non-specific values.
4. Use of plasma rather than serum can lead to nonspecific values.
5. Do not read results beyond 4 minutes.
6. Rheumatoid factors are not exclusively found in
rheumatoid arthritis but sometimes in syphilis,
systemic lupus erythromatosus, hepatitis and hypergammaglobulinemia also.
7. It is recommended that results of the tests should be
correlated with clinical findings to arrive at the final
8. QUANTIA-RF assay is sensitive to the presence of IgM
IgA with heterogenous specificity.
or infections. CRP is synthesized by the liver under
regulatory control of cytokines. Interleukins 1b and 6 and
tumor necrosis factors are the most important regulators
of CRP synthesis. The intact CRP molecule is a pentameric
protein with identical subunit arranged in a doughnut
The function of CRP is felt to be related to its role in
the innate immune system. Similar to IgG it activates
complement, binds to Fc receptor and acts as an opsonin
that enhance inflammatory response. Unlike IgG, which
specifically recognize distinct antigenic epitopes, CRP
recognizes altered self and foreign molecules based
on pattern of recognition. This recognition provides an
early defense and leads to a proinflammatory signal and
activation of the humoral immune response. CRP binds to
apoptotic cells, protects the cells from assembly of terminal
complement components and sustains an antiflammatory
rise in serum CRP, as a non-specific phenomenon. CRP
production is a non-specific response to disease and it can
never on its own be used as a diagnostic test. However,
if the CRP results are interpreted in the light of clinical
information on the patient it can provide exceptionally
Levels of CRP increase very rapidly in response to
trauma, inflammation and infection and decrease very
rapidly with the resolution of the condition. An activated
CRP is always associated with pathological changes. Hence,
determination of CRP is of great value in diagnosis, treatment
and monitoring of inflammatory condition. Measurement of
CRP may be helpful to know whether the patient is getting
better, or if there are any complications arising.
CRP Measurements Help in Diagnosis and Management
However, such symptoms may also be due to psychogenic factors. The elevation of acute
phase proteins confirms the presence of organic disease but a value within the reference range
does not exclude a mild local disease. In condition like ankylosing spondylitis, serum CRP may
be elevated before the onset of clinical symptoms
disease, levels relate to severity. Values of up to 5 mg/dL are associated with mild inflammation
and values around 10 mg/dL indicate more severe disease. Certainly CRP levels correlate more
closely with radiologically determined joint damage than other serological test. Typically, if
a patient responds to a particular drug the fall in CRP precedes the improvement in clinical
symptoms by about 6 weeks and the radiological improvement by about 6 months
organic disease such as ankylosing spondylitis
with a serious risk of eyesight. CRP rapidly falls to normal as the disease responds to therapy
in active disease. Hence, CRP levels can be used to distinguish these conditions from other
sensitive marker for bacterial sepsis. Gram-negative bacteria generally elicit more reproducible
responses than gram-positive bacteria, with modest responses to parasitic infestations and
minor responses to viruses and fungi. CRP measurement is useful in detecting infections
where clinical and microbiological diagnosis is difficult but where infection is suspected. CRP
levels relate to the extent and intensity of sepsis and successful treatment leads to decline in
often prescribed unnecessarily. It has been shown that, in children who have been ill for more
than 12 hours, a CRP level of greater than 4 mg/dL had a diagnostic sensitivity of 79%, and a
specificity of 90% for the diagnosis of bacterial infections
to the extent of tissue damage. In uncomplicated cases CRP rises above 1 mg/dL by about
6 hours, reaches a peak rarely greater than 15 mg/dL at about 48 hours, and declines
thereafter to baseline values by 7–10 days. Postoperative complications such as infections,
tissue necrosis, hematoma, and thrombosis, depending upon when they occur, will maintain
a raised CRP level after 48 hours, or result in a secondary increase. In many cases the raised
CRP precedes the clinical diagnosis of the complication pathology by up to 24 hours. In such
situations, single values are of little value and serial monitoring is essential
of 68.2% and a specificity of 75.1%
and viral meningitis in children. Bacterial meningitis is associated with higher CRP levels than
aseptic or viral meningitis. Appropriate therapy for bacterial and tuberculous meningitis causes
fall in CRP levels, and hence, this simple test can be used to monitor response to treatment with
many advantages over repeated lumbar punctures especially in children
above 10 mg/dL provides a very strong indication of bacterial infection such as purulent
bronchitis or pneumonia. Typically, viral pneumonias do not result in values above 5 mg/dL
Burns CRP levels increase significantly in patients with extensive burns. A second peak of CRP later
implies superadded infection as a late complication of burns
correlate well with peak serum levels of cardiac isoenzymes such as CKMB. In patients who
recover uneventfully the CRP levels fall rapidly towards normal. However, complications such
as persistent cardiac dysfuntion further infarction, intercurrent infection, thromboembolism,
are associated with either persistently raised CRP levels or secondary increase after initial
decrease. Angina without infarction does not stimulate CRP production. Routine assays of CRP
in patients with chest pain may thus assist in diagnosis, and management of complications
patients in acute leukemia disease process, administration of blood products, and cytotoxic therapy.
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