I suppose the test would ideally 'rule in' bacterial infections with some degree of accuracy.
Hi Matthew,
I agree to PCT testing which is in a way the best individual parameter to distinguish between viral and bacterial infections, but there are some drawbacks that are good to know.
1. There is a general bad predictive value for intracellular bacteria, in particular for respiratory infections caused by mycoplasma. Here, antibiotics may be useful, but infections may look like viral infections nonetheless.
2. Bacterial infections superinfect commonly viral respiratory infections, so in these cases there is an overlap of laboratory indicators for a viral infection followed by those indicating a bacterial infection. Here, you may be unhappier with PCT, which is not equally high as it is during pure bacterial infection.
It may be useful to refer to additional laboratory parameters such as absolute granulocyte and lymphocyte numbers, and clearly -as mentioned before- to clinical symptoms.
In conclusion, you may go better with clear advice which antibiotics to use when, instead to go with difficult conclusions driven by a difficult distinction.
In our PICU we have a good experience with Procalcitonin and also we use this biomarker for interruption of antibiotics .
Luminex corporation has a test called xTAG RVP that targets 8 viruses and subtypes and has received FDA clearance. The test could be a start to rule out viral infection. I am not aware of a test for bacterial respiratory infections for now...
Similar to Raul's answer.... There is quite a lot of research showing procalcitonin is a good marker of bacterial infection. Most of the literature focuses on identifying patients who are seriously ill (e.g. intensive care patients) who have a bacterial sepsis. However, some microbiologists in the UK are advocating its use as a test to differentiate viral from bacterial bronchitis. The premise being, avoiding inappropriate use of antibiotics on patients with viral bronchitis and therefore reducing the huge amount of antibiotic prescriptions by GPs in the UK. I think it is a great idea if the sensitivity and specificity is good enough.
Thanks all for your responses. This report from Madox on procalcitonin is useful. I work in sub-Saharan Africa and we have huge problems with antibiotic misuse. Even if the system is only semi-quantitative, one could set a broad cut-off to 'rule in' all patients with bacterial pneumonia, and accept some over-treat of patients with viral infections.
http://madox.org/horizon-scanning-reports/20120021/point-of-care-test-for-procalcitonin-to-improve-the-early-diagnosi
Procalcitonin is considered relatively specific for bacterial infections. There has been a considerable amount of work done in Switzerland on the use of procalctonin for differentiating bacterial and viral respiratory infections (I can give a few links if needed).
I don't know if there are "point of care" format tests for procalcitonin on the market.
This seems to be the only one
http://www.procalcitonin.com/default.aspx??tree=_4_7&key=products2
We have a lot of experience with procalcitonin and C reactive protein for diagnosis of bacterial sepsis, prediction of outcome and interruption of antibiotics. In general, procalcitonin performed better than C reactive protein because of more rapid cinetic, and more specificty in cases of trauma, burns, postoperative...
PCT and CRP are markers of inflammation more than infection; therefore, the information they give is usefull but cut-off levels are different when the possibility of other source of inflammation, apart from the infection, is present,
For me is important the use of procalcitonin to differ bacterial and viral infection, and to decide the lenght of antibiotic therapy.
Can PCT be used to monitor the decrease of bacterial infection during antibiotics treatment (to verify efficacy of the therapy)?
When PCT is a inflammation marker, does that mean that viral infection never causes inflammation (PCT being distinctive)?
Yes, it's also very good to verify the efficacy of the therapy. PCT rarely is elevated in viral infections; pay attention to false positive!!!!
When antibiotic treatment is controling bacterial infection a rapid decrese in PCT levels is observed. Aproximattely, half of the previous value every 24 h.
Inflammation due to viral infection is much less intensive than inflammation due to a viral infection. But some virus in certain cases, for example adenovirus can increase PCT levels at values between 0,5 and 1,0 ng/mL.
Hi Matthew, I am a bit slow on the ball here as only get to see the questions in my inbox about 2 days later! Quite new at this!
I am an application specialist working for the diagnostic company bioMerieux. We offer a PCT test that can be used on the VIDAS systems if your workplace has one, otherwise you can speak to a bioMerieux representative there. One of the reasons for having this test was to promote it as a point of care test as you indicate. I will try to send you 2 attachments regarding PCT testing. I hope you receive these and they are useful to you. Please let me know if you do not receive them and if I can be of any further assistance on this if necessary.
Article Surviving Sepsis Campaign: International Guidelines for Mana...
Hi Matthew,
I agree to PCT testing which is in a way the best individual parameter to distinguish between viral and bacterial infections, but there are some drawbacks that are good to know.
1. There is a general bad predictive value for intracellular bacteria, in particular for respiratory infections caused by mycoplasma. Here, antibiotics may be useful, but infections may look like viral infections nonetheless.
2. Bacterial infections superinfect commonly viral respiratory infections, so in these cases there is an overlap of laboratory indicators for a viral infection followed by those indicating a bacterial infection. Here, you may be unhappier with PCT, which is not equally high as it is during pure bacterial infection.
It may be useful to refer to additional laboratory parameters such as absolute granulocyte and lymphocyte numbers, and clearly -as mentioned before- to clinical symptoms.
In conclusion, you may go better with clear advice which antibiotics to use when, instead to go with difficult conclusions driven by a difficult distinction.
Thanks Hauke, that is very useful info! I take it that the specificity of PCT for bacterial infection in the widest sense is not that high then. Lots of caveats and restricted to certain bacterial species......
Not exactly what you wanted but quite new: Circulating galectin-3 in infections and non-infectious inflammatory diseases. Eur J Clin Microbiol Infect Dis. 2013 Jul 5.
If you work with real time PCR to detect or quantify different bacterias or viruses typical of respiratory infections, you could find out which specie/s is/are implicated.
I have a lot of experience with Septifast system from Roche Diagnostics for sepsis patients. The main advantage is that in a few hours you have the result. The most important factors to obtain good results are: short preanalytical time, kind of sample, DNA/RNA extraction system, in house or kit RT multyplex PCR. You can do all in 5 hours.
Hi Enrique,very well. This is where the future is!
However,lots of samples are not sterile anyway.
How do you handle lower copy numbers of potentially pathogenic bacteria? do you have experience with cut-offs which amount of which bacteria is indicating a relevant infection?
do you treat patients until you get results from antibiogram according to best species-specific probabilities?
Point of care diagnostic test for differentiation of bacterial and viral respiratory infection: the test is available: PCR but one has to clinically diagnose to choose one and rule out.
In case of bacterial infection one can go for prophylaxis based on suspision eg: Streptococcal infection etc.,
Grams stain of throat swab and sputum may give a hint on what bacterial cause could be
Nasopharynx swab, throat swab, and sputum may be the better samples.
KIT diagnostis tests better than in house ones because sterile conditions.
You could quantify copy number of viral particles or bacterias, and of course if there are thousands or more probably may be the infection cause. If there are less than hundreds may be contamination. You have to standarized an umbral cycle of RT PCR depending of the sample, DNA/RNA extraction system, etc, ...
Our concordance between blood cultures and SEPTIFAST is around 90%.
CRP is in my opinion the best available POC test at this moment, most studies evaluatie the rationale for the prescriptions of antibiotics (ie bacterial infections) and show that a POC CRP test indeed has added value.
Yes, CRP to some extent - there is a Cochrane review by Rune aabenhus et al. coming up on the topic.
CRP is the least specific biomarker that I ever came across: It is an inflammatory marker, but it also goes up with Alzheimer, with mental stress and depression. And of course with cardiovascular diseases and who knows what else. I would be surprised if it would distinguish bacterial from viral infection.
I would go for procalcitonin, but not alone, unless I want to de-escalate or discontinue antibiotic therapy. A combination of procalcitonin with neopterin would be useful since the latter overcomes the problems noted by Hauke Walter regarding the intracellular bacteria. Furthermore, it seems promising also for viral infections, too. I hope I helped.
I think it depends on the setting (what is the probability of bacterial infection in your population of patients and which pathogens are encountered) and personal experience.
Not all bacteria cause leukocytosis (streptococci and sometimes E coli do that) so if you work in a setting with high pneumococcal vaccination coverage then the prevalence of pneumococcal infections is low and WBC count is not so useful. Research has shown PCT to be comparable to CRP. I believe PCT is superior (rises more quickly) in first 12 h of infection and after that they are more or less the same. Then there is the LAB score that uses CRP, PCT and urine - it is used in pediatric setting.
But you should not rely exclusively on the laboratory - you should ask all the right questions and take a good look at the patient. And also, do not forget your instincts - because (and this has been proven scientifically by van den Bruel et al, BMJ 2012) if a doctor has a gut feeling that something is wrong with the patient despite a normal clinical exam, he/she should do additional tests or refer the patient for further workup.
Question: How would you distinguish Procalcitonin rise in a Cancer patient? Example, Calcitonin is the marker for Medullary Thyroid Cancer and Procalcitonin is produced as a precursor to Calcitonin. Then add imaging showing slow growing mets in the lungs too small to biopsy.
In that case you can go for a combination of procalcitonin with neopterin. Though the reports of neopterin are fewer, you can try the same.
To my knowledge, there is no POC diagnostic test available. In general you have two choices 1) immunofluorescence for viral/bacterial pathogens which will have to be carried out in a panel style, and 2) PCR based which again would ideally be a multi-plex for both viral/bacterial pathogens.
There is a company called Biofire that has a multiplex panel (called "Filmarray") for respiratory pathogens. It differentiates between 18 viruses and 3 bacterial (Atypical pneumonia causing) pathogens. It is fast, it hink between 1-3 hours and is FDA approved.
PCT is good but still requires clinical co-relation as well as co-relation with other laboratory parameters (which may not be too specific).
I hope this helps.
Hi,
you can try PCT, CRP etc, but you can`t differentiate between bacterial and viral respiratory infections. In our hospital (emergency department of children) we use POC test, mariPOC (http://arcdia.com/eng/maripoc/introduction/) Please read also my publication "Bacterial coinfections in children with viral wheezing" in Eur J Clin Microbiol Infect Dis 2006
-Pasi Lehtinen-
Hi Oliver,
I am aware that those tests are not POC tests. I just wanted to add extra information, in case it was needed. Thanks anyway!!
Regards,
Michael.
Hi Michael
More information from our POC-test (multianalyte antigen detection). This novel point-of-care test system is a rapid, practical, and specific method for simultaneous detection of eight respiratory viruses. Compared with RT-PCR, its sensitivity is moderately high for detection of RSV and influenza viruses, and low for adenovirus. Read more in publication Ivaska et al. Identification of respiratory viruses with a novel point-of-care multianalyte antigen detection test in children with acute respiratory tract infection. J Clin Virol 2003
Regards -Pasi-
There is increasing evidence that C reactive protein (CRP) can be used in primary care as a a point of care diagnostic test to differentiate between bacterial and viral respiratory infections. The majority of antibiotics (about 90%) are prescribed by a general practitioner (GP). CRP testing has a rather high sensitivity and a negative test (CRP
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