The Value of C-reactive Protein in Primary Health Care

POC
The Value of C-reactive Protein
in Primary Health Care
2
POC
The Value of C-reactive Protein
in Primary Health Care
3
Disclaimer
This booklet is intended to provide health care practitioners with an overview of QuikRead CRP, a rapid C-reactive
protein assay, its diagnostic potential and value in routine primary care practice.
Although every effort has been made to provide accurate information, Orion Diagnostica accepts no responsibility whatsoever for the accuracy, correctness or completeness of the information contained in this booklet. It is
the responsibility of the health care practitioner to evaluate the contents of this booklet and to verify the information presented. The ultimate judgement regarding the care and appropriate treatment of a particular individual
must always be made by the health care practitioner in the light of all the clinical information available about the
individual.
Orion Diagnostica therefore accepts no liability for any injury or damage to person or property resulting from
acceptance of the information in this booklet. Hence, liability claims regarding possible injury or damage will be
rejected.
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regulatory authorities in your country. Orion Diagnostica assumes no responsibility for you accessing information
that may not comply with legislation, regulations or usage applicable in your country. You are advised to consult
Orion Diagnostica’s local business contact or marketing partner for information about the availability of Orion
Diagnostica products in your country.
4
Contents
Introduction................................................................................... 7
Antibiotic use and resistance.......................................................... 8
Antibiotic resistance on the rise......................................................................... 8
Development of new antibiotics on the decline.................................................. 9
Variation in antibiotic use and antibiotic resistance among countries................ 10
C-reactive protein (CRP)............................................................... 11
CRP in distinguishing between bacterial and viral infections............................. 11
CRP in monitoring the efficacy of antibiotic therapy......................................... 12
CRP versus erythrocyte sedimentation rate (ESR).............................................. 13
CRP versus white blood cell count (WBC)......................................................... 13
CRP versus procalcitonin (PCT)......................................................................... 13
CRP is a good servant...................................................................................... 13
QuikRead CRP guides the use of antibiotics.................................. 14
Diagnostic dilemma......................................................................................... 14
QuikRead CRP................................................................................................. 14
Interpreting the QuikRead CRP test result..................................... 16
QuikRead CRP in various clinical situations................................... 17
Serious bacterial infections.............................................................................. 18
Acute respiratory tract infections..................................................................... 18
Upper respiratory tract infections.............................................................. 19
Common cold..................................................................................... 19
Acute sinusitis..................................................................................... 19
Acute pharyngitis................................................................................ 19
Acute otitis media............................................................................... 20
Lower respiratory tract infections.............................................................. 20
Acute bronchitis................................................................................. 20
Community-acquired pneumonia........................................................ 21
Urinary tract infections.................................................................................... 22
QuikRead CRP in the routine diagnosis of
acute respiratory tract infection.................................................... 23
References................................................................................... 26
5
6
Introduction
This booklet is intended to give primary care practitioners an overview of
QuikRead® CRP, a rapid C-reactive protein (CRP) assay, its diagnostic potential and value in routine practice. The emphasis is on situations in which
an immediately available, quantitative CRP result can help to make adequate
and timely diagnostic and treatment decisions.
CRP is a protein normally present in very low concentrations in the
blood of healthy people. In bacterial infections, CRP concentrations markedly increase, whereas viral infections usually only induce very modest CRP
elevation or none at all.
In primary care, a large proportion of antibiotics is prescribed to treat
conditions in which antibiotics are of little or no benefit. Excessive and
inappropriate use of antibiotics, leading to the emergence of increasingly
resistant bacteria, has become a severe problem worldwide. Against this
background, the individual health care practitioner often faces the dilemma
of how to identify patients who need – and particularly those who do not
need – antibiotic therapy.
QuikRead CRP is an easy-to-use test for quantitative measurement of
CRP. The test is designed to be performed on a finger-prick blood sample and
the test result is available in a couple of minutes during the patient consultation. QuikRead CRP is a valuable tool helping the primary care practitioner
to distinguish between bacterial and viral infections and to target antibiotic
treatment to patients most likely to benefit from it.
7
Antibiotic use and resistance
Antibiotics are a cornerstone for the management of bacterial infections.
Therefore, antibiotics should be used with caution and only when absolutely
necessary.
Like all medicines, antibiotics can cause side effects. The most common
side effects are generally considered to be mild, and include conditions such
as headache, dizziness, gastrointestinal upset, nausea and vomiting.1,2,3
However, antibiotics may alter the normal microbial flora of the patient
and lead to acute or even chronic disease in some individuals.4,5,6,7,8,9,10 The
effects of antibiotic treatment on the native gut microbial flora are well
established and range from self-limiting mild diarrhea to life-threatening
pseudomembranous colitis.11,12,13,14 Vaginal yeast infections are also common
after taking antibiotics.15,16,17,18 Being a cause for concern and discomfort for
many women, they may even be a reason for not wanting to take prescribed
antibiotics.15 Even a short-term antibiotic course can cause long-term alterations in the commensal microbial flora of the individual patient4,5,6,19, and
therefore unnecessary antibiotic courses should be avoided.
Antibiotics can also cause allergic reactions ranging from skin rash to
severe life-threatening attacks that require immediate medical attention.20
Other serious adverse reactions that warrant for the judicious and cautious
use of antibiotics include alterations in blood glucose levels, QTc interval
prolongation, seizures, phototoxity and tendinopathy.3,21
Recently, antibiotic use in early life has also been linked to childhood
asthma.22,23,24
Antibiotic resistance on the rise
Frequent use of antibiotics results in antibiotic resistance which is one of the
most serious public health concerns today.25–28 A strong correlation between
frequent use of antibiotics and a rising rate of antibiotic resistance has been
established in many studies (Fig. 1).27, 29–31
8
Penicilli-nonsusceptible S. pneumoniae (%)
Total antibiotic use (DDD/1,000 pop/day)
Fig. 1. Total antibiotic use in the out­patient
setting versus prevalence of penicillinnonsusceptible Streptococcus pneumoniae in
20 industrial countries. DDD = defined daily
doses.30
Antibiotic-resistant bacteria have steadily increased and present a threat to
disease management32 not only in hospitals but also in primary care.33 Many
previously effective antibiotics are now ineffective, and the appearance of
multidrug-resistant bacteria is contributing substantially to the problem.26,32–34
About 80–90% of antibiotics are prescribed within primary care27,35–37,
and as many as 50% of these prescriptions are likely to be unnecessary.33,36
Moreover, broad-spectrum antibiotics are substantially overused, even for
conditions where antibiotic therapy is not indicated at all, a practice additionally driving up resistance problems.38,39
Development of new antibiotics on the decline
Development of new antibiotics is not keeping pace with the increase of antibiotic resistance. Despite the critical need for new antibiotics, the development
of these drugs is declining.25,31,32,40 It is estimated that the development of a
new antibiotic takes 10–15 years from discovery to approval.31,41
9
Variation in antibiotic use and antibiotic resistance
among countries
The use of antibiotics in primary care differs among countries (Fig. 2), which
is unlikely to be caused by differences in frequencies of bacterial infections.42
Antibiotic-prescribing practices, attitudes towards antibiotic use and regulatory control of prescribing have been found to have an impact on the prevalence of antibiotic-resistant bacteria.28,42–45
Most antibiotic prescriptions in primary health care are for acute respiratory tract infections. Antibiotic treatment of these conditions is, however,
often inappropriate, since the vast majority have a viral cause (see Acute
respiratory tract infection, page 15). A diagnostic test providing an objective
and immediate result that confirms or rules out a viral infection could have
an important role in ensuring more precise diagnoses and reducing inappropriate use of antibiotics.
Other antibacterials (J01X)
Aminoglycosides (J01G)
Amphenicols (J01B)
35
Quinolones (J01M)
MLS (J01F)
25
Tetracyclines (J01A)
Cephalosporins (J01D)
20
Penicillins (J01C)
15
10
† = Total use; ‡ = 2005 use;
TMP = Trimethoprim; MLS = Macrolides, Lincosamides and Streptogramins
Fig. 2. Outpatient antibiotic use in 21 European countries in 2006. DDD = defined daily doses.46
10
Russia
Austria
Netherlands
Slovenia
Denmark
Sweden ‡
Hungaria
Czech Republic
Finland
Bulgaria †
Spain ‡
Iceland
Poland ‡
Ireland
Croatia
Portugal
France
Cyprus †
Greece † ‡
0
Italy
5
Belgium
DDD / 1000 inabitants / day
TMP and sulphamides (J01E)
30
C-reactive protein (CRP)
CRP is an acute-phase protein synthesised in the liver. CRP concentrations are
normally low in the blood of healthy people; 99% have levels under 10 mg/ll47
which is generally considered as the cut-off for inflammatory disease48-51 (see
also QuikRead CRP in various clinical situations, page 14).
Production of CRP is rapidly induced by cytokines in response to infection, inflammation and tissue injury.47,52,53 Elevated CRP concentrations can
be detected within 6–12 hours of the onset of an inflammatory stimulus54,55,
and the concentrations peak within 24–48 hours.47,51,56 The elevation can even
be more than 1000-fold.47,57, 58
CRP has been found to reflect closely the extent, activity and severity
of disease.47 With resolution of an infection or inflammatory process, CRP
levels decline rapidly owing to the short half-life (19 hours) of CRP in the
bloodstream.47,51
Although elevated CRP concentration is not specific to any particular
disease, quantitative measurement of CRP adds valuable information to the
diagnosis, treatment and monitoring of an inflammatory process and the
associated disease.
In a primary care setting, CRP can assist doctors in
• distinguishing between bacterial and viral infections
• monitoring the efficacy of antibiotic therapy.
CRP in distinguishing between bacterial and viral
infections
Combined with careful clinical assessment, CRP can help
to differentiate bacterial infection from viral infection.
CRP levels are increased markedly by invasive
bacterial infection. 50–85% of patients with a CRP
CRP levels
are increased
markedly by
invasive bacterial
infection.
concentration exceeding 100 mg/l will have a bacterial
infection.58–60 Acute Gram-positive and Gram-negative
11
bacterial infections are among the most potent stimuli for CRP production.47
Bacterial infection without a clearly elevated CRP concentration is unlikely but may occasionally be encountered. Patients may have low or only
moderately elevated CRP concentrations if the sample is taken during the
first 6–12 hours after onset of the infection. Therefore, a normal CRP value
on the first day of illness should be interpreted with caution.55 CRP results
should also be interpreted with great care in the early neonatal period. The
amount of CRP produced depends on the invasiveness and location of the
infection in the body. Superficial or localised, minor bacterial infection may
not stimulate CRP production significantly.47
Uncomplicated viral infection usually has little effect on CRP concentration.47 A moderately elevated CRP concentration (10–60 mg/l) may, nevertheless, be found in some upper respiratory tract infections with a peak
during days 2–4 of illness.55,61 The elevation may, however, in
some cases reflect secondary bacterial infection.47 Higher
CRP values can be found in infections caused by adenoviruses.62 In patients with signs and symptoms of common
cold, a minor part of cases are, however, associated with
adenoviruses.63-65
Uncomplicated
viral infection
usually has little
effect on CRP
concentration.
CRP in monitoring the efficacy of
antibiotic therapy
CRP concentrations drop rapidly, at roughly 50% a day51, in response to
effective treatment. Serial measurement of CRP is therefore of great value in
monitoring the effect of antibiotic therapy, and antibiotics can usually be stopped upon normalisation of the CRP value.47,51,66,67
Serial measurement
of CRP is of great
value in monitoring
the effect of
antibiotic therapy.
12
In contrast, inadequate treatment is reflected in persistently
high CRP levels which may even rise further if the infection takes a turn for the worse.47,59 Monitoring of CRP
concentration can alert to complications and predict the
outcome earlier than clinical signs.68
CRP versus erythrocyte sedimentation rate ESR
ESR is a nonspecific inflammation marker and a commonly performed
laboratory analysis.47,69 CRP has many advantages over ESR. ESR is greatly
influenced by the size, shape and number of erythrocytes, gender and age of
the patient, as well as serum proteins such as fibrinogen and immunoglobulins.
Therefore, ESR results can vary and sometimes mislead.58 As a patient’s condition worsens or improves, ESR changes rather slowly, whereas plasma CRP
concentration reacts rapidly.58,70 ESR is also greatly affected by technical factors, such as assay temperature, sample dilution and tilting of the ESR tube.69
CRP versus white blood cell count WBC
CRP has been found to be more sensitive and specific than WBC for differentiation between bacterial and viral infection.71-73 In young febrile children,
CRP is superior to WBC in predicting which febrile children have occult
severe bacterial infection74-77 requiring antibiotic therapy. WBC values are
also not consistent enough to be used in monitoring the effect of antibiotic
treatment in bacterial infections.68
CRP versus procalcitonin PCT
Similarly to CRP, PCT is a general marker of bacterial infection.73,75,76,78-83
However, PCT measured at central laboratory is not ideal for routine primary
care84-86 where timely results often are needed to support therapy decisions.
CRP is a good servant
CRP must not be used as the only measure of a patient’s condition. Yet, interpreted in the context of the patient’s symptoms and history, a timely CRP
result is a substantial aid helping the health care practitioner reach the right
diagnosis and correct treatment decision.
13
QuikRead® CRP guides
the use of antibiotics
Diagnostic dilemma
The primary care practitioner has to make
judgement on the cause of patients’ infections more or less every day. A key question is whether the presenting symptoms
are related to a serious bacterial infection
requiring antibiotic treatment or a benign,
self-limiting viral illness.87,88
The clinical signs and symptoms of
patients with bacterial and viral infections frequently overlap and may not
clearly differentiate between these groups of patients.54,87-93 This, together with
pressure from patients, time constraints and the lack of diagnostic tools, may
lead to prescription of unnecessary antibiotics.44,94-96
Although a sample or the patient may be sent to a laboratory for testing,
a test result that is received hours or days later seldom has any effect on the
treatment decision or the course of treatment. Today’s technology allows the
health care practitioner to rapidly perform a diagnostic test and obtain the
result during patient consultation without unnecessary delay.97
QuikRead CRP
QuikRead CRP is an easy-to-use test for quantitative measurement of CRP
on a finger-prick blood sample. The system – consisting of a small portable
instrument and a ready-to-use kit – is especially designed for use in the primary
care setting. When the test is performed near the patient, the result will be
available in a couple of minutes during the patient consultation to support
diagnosis and therapeutic decision-making.
14
In combination with patient history, physical examination and careful
clinical judgement, QuikRead CRP is a valuable tool assisting the health care
practitioner in differentiating between viral and bacterial infections.
A clearly elevated QuikRead CRP result indicates bacterial infection
warranting antibiotic treatment. Conversely, QuikRead CRP can also provide reassurance to both the health care practitioner and the patient in cases
where prescription of antibiotics does not appear justified. By confirming a
likely viral infection, QuikRead CRP can help to reduce unjustified use of
antibiotics98 particularly in connection with respiratory tract infections.99-101
Avoidance of unnecessary antibiotic use will substantially reduce the number
of patients who experience antibiotic-associated adverse events.20 Appropriate
use of antibiotics may also contribute to slowing down or even reversing the
development of antibiotic resistance.102,103
QuikRead CRP provides a reproducible and quantitative result that is as
accurate as that obtained using clinical chemistry analyzers.98,104-107
QuikRead CRP features
• assists in differentiating between viral and bacterial infections
• immediate test result allows the treatment decision to be made during
patient consultation
• small finger-prick blood sample convenient for the patient
• aids in targeting antibiotic therapy to patients most likely to benefit from it
• contributes to reducing unjustified antibiotic prescribing in respiratory tract
infections
• allows monitoring of the efficacy of antibiotic therapy
• simple to operate, easy to read, no special laboratory skills required
• consistent day-to-day results
• quantitative CRP result within the range 5–200 mg/l for QuikRead go and
within the range 8–160 mg/l for QuikRead 101
• comparable to clinical chemistry analysers in accuracy
• in-built calibration
• instrument requires minimum servicing
15
Interpreting the QuikRead® CRP
test result
Optimally, a diagnostic test should have high sensitivity (= the ability of the
test to correctly identify diseased individuals) and high specificity (= the ability
of the test to correctly identify non-diseased individuals).
A cut-off point – a clinical decision threshold – is usually set to discriminate
between diseased and non-diseased individuals. As diagnostic tests, however,
rarely demonstrate 100% sensitivity and specificity, using any single value
as a cut-off will usually cause some overlap, yielding following categories
of test results:
• True positive (TP) = a positive/abnormal test result on a diseased individual
• True negative (TN) = a negative/normal test result on a non-diseased
individual
• False negative (FN) = a negative/normal test result on a diseased individual
• False positive (FP) = a positive/abnormal test result on a non-diseased
individual
Test with low cut-off
Test with high cut-off
• high sensitivity, low specificity
• high specificity, low sensitivity
• likely to identify all diseased
• likely to identify all non-diseased
individuals
• negative/normal result indicates
non-diseased individual: the
disease can be excluded
• will give some false positive results
individuals
• positive/abnormal result indicates
a diseased individual: the disease is
confirmed
• will give some false negative results
The positioning of the cut-off affects both the sensitivity and specificity
of the test (Fig. 3). When the result of a quantitative test such as QuikRead
CRP is interpreted, various cut-off levels may be set depending on what is
considered optimal for each condition – as evidenced by the clinical examples
cited in the following chapter.
16
A low CRP cut-off is generally used to exclude infections of bacterial aetiology. On the other hand, a high CRP cut-off is needed to confirm
bacterial aetiology of an infection. Low and high cut-offs also can be used
simultaneously. Results falling between the cut-offs (“grey area”) require
special consideration.
Fig. 3. Effects of changing the cut-off point of a diagnostic test.108 By permission of Cambridge University Press.
As with any diagnostic test, the QuikRead CRP test result should always
be evaluated in the light of all clinical findings before making the final diagnosis and therapeutic decision.
QuikRead® CRP
in various clinical situations
The following sections discuss the value of QuikRead CRP in various clinical
situations with emphasis on infections commonly encountered in primary care.
17
Serious bacterial infections
Septicaemia, endocarditis, osteomyelitis, septic arthritis, bacterial pneumonia
and meningitis as well as pyelonephritis are usually associated with markedly
elevated CRP concentrations.70,71,73,92,109-119
Measurement of CRP is also useful in the management of feverish conditions without localising signs. Fever is a common symptom in self-limiting,
benign viral illness. However, some febrile patients without apparent source
of infection may have an occult severe bacterial infection that a CRP test
can help confirm.74-76,115
CRP > 10–20 mg/l has
been regarded as
elevated. 66,67,70-
CRP < 50 mg/l may
rule out serious
bacterial infection.73,74
CRP > 100 mg/l suggests severe bacterial
infection.55,60,73,120
77,109,114,117,119
Acute respiratory tract infections
Acute respiratory tract infection (ARTI) is the most frequent reason for
seeking medical attention in primary care121, 122, also accounting for most
antibiotic prescriptions.27,36,37,100,121-126 ARTIs are caused by viruses, bacteria
or a combination of both, and cases of different aetiology often present with
similar symptoms. Identifying patients with a viral infection and patients
suffering from a bacterial infection requiring antibiotics is therefore a daily
challenge in primary health care.
18
Upper respiratory tract infections
Common cold. The common cold is a viral illness in which symptoms like runny nose, sneezing, sore throat and cough are present but not prominent. The
common cold usually resolves spontaneously, although a small
Uncomplicated
viral infections
mostly induce very
modest elevation
of CRP concentration
or none at all.47
proportion may be complicated by bacterial co-infection.127,128
Despite the viral origin, antibiotics are widely prescribed for
patients with the common cold.100,127-129
A normal CRP concentration can help to identify
patients with the common cold for which antibiotics are
not indicated.
Acute sinusitis. Most cases of sinusitis are viral and
uncomplicated but patients are frequently prescribed antibiotics. 90,130-132
Up to 90% of patients with a cold exhibit symptoms of sinusitis in the early
stages of their illness but only a minor part develop bacterial sinusitis.130,133
Bacterial and viral sinusitises are difficult to differentiate based
on clinical symptoms and signs only.54,80,91 Measurement of
CRP assists in diagnosing bacterial sinusitis and in deciding
whether to prescribe antibiotics to a patient with symptoms
of sinusitis.54,100,134
Implementing the CRP test in primary care may lead
CRP > 10-50 mg/l
may suggest
bacterial
sinusitis.55,130,135
to reduction in antibiotic prescribing to patients with
sinusitis.54
Acute pharyngitis. Most cases of acute pharyngitis are caused by viruses. The
most common bacterial cause of acute pharyngitis is Streptococcus pyogenes,
also known as group A ß-haemolytic streptococcus (Strep A). Strep A infection is the only commonly occuring form of sore throat warranting antibiotic
treatment.136-139
Only a minority of sore throats in adults are caused by Strep A, while
children have a higher incidence.136–141 Antibiotics are nonetheless prescribed
to most patients140-142, often to avoid such potentially severe, but nowadays
rare, complications as rheumatic fever and acute glomerulonephritis.139,143
19
A CRP concentration of 35 mg/l
is a useful cut-off point
for differentiating
bacterial and
nonbacterial
pharyngitis.89
As the signs and symptoms of Strep A infection and
those of pharyngitis caused by other micro-organisms
(most commonly viral) often overlap137,138, it is difficult to
make an accurate diagnosis on clinical grounds only.89 To
avoid inappropriate antibiotic treatment of large numbers
of patients with pharyngitis, it is important to verify or
exclude Strep A infection using a diagnostic test136,137,
such as the QuikRead Strep A test.
An immediately available CRP result may also increase the proportion of
sore-throat patients diagnosed correctly and treated adequately.89 Elevated
CRP concentrations have been found in patients with Strep A pharyngitis.89,144-146
Acute otitis media. The incidence of acute otitis media (AOM) is highest
between the ages of 6–12 months147,148, and more than 70% of
children have AOM before their second birthday147.
AOM is generally considered to be a bacterial infection149,150, although also viruses seem to have a role in the
development of AOM.149 Bacterial and viral AOM cannot
CRP > 20 mg/l may
suggest bacterial
otitis media.151
be differentiated on clinical signs and symptoms alone.151
An elevated CRP concentration has been found to
suggest bacterial AOM.151
Lower respiratory tract infections
Acute bronchitis. In acute bronchitis cough is the most frequently observed
symptom, and the illness usually lasts one to three weeks. 152–154 About
70–95% of cases of acute bronchitis are caused by viruses.152,155,156 Bacterial
aetiology has been established in only about 5–10% of patients with acute
bronchitis.152,155
Despite its overwhelmingly viral nature, an estimated 50–90% of doctor’s
office visits for acute bronchitis result in an antibiotic prescription.152,153,157,158
There is little evidence to support the effectiveness of such an approach in
20
CRP < 10-11
mg/l is usually
found in patients with
bronchitis of viral origin61,162,163 and excludes
bacterial CAP.161,163,164
acute bronchitis88,152,156,159, and routine antibiotic treatment
of this illness is therefore not recommended.152,155,159
The evaluation of patients should focus on ruling
out community-acquired pneumonia (CAP) caused by
bacteria.92,152,155,160 Quantitative measurement of CRP
can help to distinguish acute bronchitis from bacterial
CAP.92,154,161 Low CRP concentration along with a history
and clinical findings suggesting a viral infection indicates
that antibiotics are not needed.
Community-acquired pneumonia. A wide variety of viruses, bacteria and
atypical agents can cause community-acquired pneumonia (CAP).165,166
While antibiotics are seldom required for acute lower respiratory tract
infections, which are to a great extent of viral origin, antibiotics are nearly
always indicated for bacterial CAP. A delay in treatment of bacterial CAP
increases the risk of a fatal outcome.167
The prevalence of bacterial CAP is about 5% among patients suspected
of having the infection.160,167
In primary care, CAP is often diagnosed on the basis of symptoms and
physical examination alone, which may be insufficient to identify patients
with bacterial CAP requiring antibiotic treatment. 73,92,93,125,160,161 This is
particularly true in primary care because of the lower incidence and lower
severity of CAP found there.92
Quantitative measurement of CRP in combination with patient history
and clinical findings can contribute to the diagnosis of CAP.55,73,92,125,161,163,167-171
Patients with confirmed bacterial CAP have considerably higher CRP
levels than patients with other acute lower respiratory tract infection.161,163,171
High CRP values may also correlate with disease severity, which may be of
value in deciding about the necessity of inpatient care.163 CRP is also useful
in monitoring the response to antibiotic therapy.161,170
21
CRP < 20 mg/l:
antibiotics are not
indicated in low-risk
patients.92
CRP < 10–11 mg/l:
bacterial CAP can
usually be ruled
out.55,161,163,164
CRP > 100 mg/l:
strong indication
of bacterial
CAP.56,73,161,164,170,171
CRP < 50 mg/l:
antibiotics can often
be withheld.73,125,167
CRP 50–100
mg/l: chest X-ray,
new consultation
within 1-2 days or
prescription of
antibiotics, depending
on the clinical
situation.125
Urinary tract infections
Acute uncomplicated cystitis (lower urinary tract infection) is one of the
most common bacterial infections.172-174 As almost 80–90% of uncomplicated
urinary tract infections in primary care are caused by Escherichia coli172,175,
typical clinical cases are usually managed with minimal evaluation and routine
prescription of an antibiotic.176,177
The most severe form of urinary tract infection is acute pyelonephritis
(upper urinary tract infection), which is associated with significant shortterm morbidity and can cause permanent renal damage.174 If pyelonephritis
is suspected, further investigation is required.
While increased CRP concentration is seldom encountered
in patients with acute uncomplicated cystitis, it is commonly found in patients with acute pyelonephritis.119,178
Quantitative measurement of CRP therefore provides
diagnostic support for differentiating between cystitis
and pyelonephritis. A high CRP concentration in a patient
with urinary tract infection indicates the possibility of
pyelonephritis.119,178-180
22
CRP > 20–40 mg/l
suggests
pyelonephritis.176,178,181,182
QuikRead® CRP in the
routine diagnosis of
acute respiratory tract infection
The decision tree on the following page illustrates potential courses of action
when QuikRead CRP is used to support clinical decision-making in acute
respiratory tract infection.
In this scheme, a CRP concentration of 10 mg/l is used as the clinical cutoff for excluding bacterial infection, although it may lead to overdiagnosis
and unnecessary treatment in some patients without bacterial infection. The
health care practitioner is therefore advised to set an optimal cut-off value
for each condition to achieve the best possible treatment outcome.
An increase in CRP concentration between successive measurements is
usually a sign of the patient’s infection having taken a turn for the worse. A reduction in CRP concentration, on the other hand, is a sign of patient recovery.
This decision tree should be considered only a guide for clinical decisionmaking and should never be relied upon as a substitute for professional
medical judgement.
23
The decision tree
Asthma, allergy, COPD etc
ruled out
ACUTE RESPIRATORY
TRACT INFECTION
Clinical signs,
duration of symptoms
CRP <10 mg/l
Probable viral
cause
Measure CRP
CRP >10 mg/l
Probable bacterial
cause
Patient
recovers
Most likely
bacterial cause
CRP >50 mg/l
Antibiotic prescription
(if clinical picture
requires)
Patient
recovers
Symptomatic
treatment
Patient returns:
symptoms persist /
turn to worse
Patient returns:
symptoms persist /
turn to worse
CRP >10 mg/l
Measure CRP
Measure CRP
CRP <10 mg/l
Additional
investigations /
treatment based on
clinical picture
Patient recovers
24
CRP <10 mg/l
*)
Additional
investigations / possible
change of antibiotics
*) CRP increased compared to previous
measurement / not considerably decreased
The QuikRead® CRP System
QuikRead 101 Instrument
and QuikRead CRP kit with buffer bottle
QuikRead 101 Instrument
and QuikRead CRP kit with prefilled cuvettes
Please also visit
www.quikread.com
QuikRead go Instrument and QuikRead go CRP kit
25
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
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17.
18.
19.
26
Dancer SJ. How antibiotics can make us sick: the
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Scott LJ et al. Cefuroxime axetil: an updated review of its use in the management of bacterial
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Oliphant CM and Green GM. Quinolones:
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Löfmark S et al. Clindamycin-induced enrichment
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2006;58:1160-7.
Jernberg C et al. Long-term ecological impacts of
antibiotic administration on the human intestinal
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De La Cochetière FM et al. Resilience of the
dominant human fecal microbiota upon shortcourse antibiotic challenge. J Clin Microbiol
2005;43(11):5588-92.
Xu J, Sobel JD. Antibiotic-associated Vulvovaginal
Candidiasis. Curr Infect Dis Rep 2003;5(6):481-7.
Bartosch S et al. Characterization of bacterial
communities in feces from healthy elderly volunteers and hospitalized elderly patients by using
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