Questions about neutrophils
I've read different places that neutrophils are primarly increased with bacterial and fungal infections. According to Wikipedia they 'defend against bacterial and fungal infection'.
Given that a patient has increased CRP levels, but not high enough to let you know that it's most likely a non-viral infection. You also measure leukocytes and find that the patient has increased neutrophils and monocytes, but no increase in lymphocytes. Can the test result on the different types of leukocytes be used as an indicator for a non viral cause of infection like bacterial or fungal?
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According to Leukocytosis (Emedicine), in general:
Neutrophils are high in bacterial and low in viral infections.
Exceptions: Neutrophils can be low in some bacterial infections, such as typhoid fever, rickettsial infections, brucellosis, dengue, Staphylococcus aureus, tularemia, Mycobacterium tuberculosis, ehrlichiosis and leishmaniasis (American Family Physician, Emedicine).
Lymphocytes are high in viral and low in bacterial infections.
Exception: Lymphocytes can be high in bacterial infections, such as pertussis
Monocytes are high in bacterial infections (tuberculosis, subacute bacterial endocarditis, brucellosis, syphilis) and many protozoal and rickettsial infections (eg, kala azar, malaria, Rocky Mountain spotted fever), and normal in viral infections.
Exception: Monocytes are typically high in infectious mononucleosis and in some other viral infections.
Other markers:
CRP tends to be higher in bacterial than viral infections, but low CRP does not rule out bacterial infections (Scand J Infect Dis. 1993).
Procalcitonin: Bacterial infection is unlikely if procalcitonin is <0.25 ?g/l and very likely if it is >0.50 ?g/l (Annals of Rheumatic Diseases, 2003 ; BMC Medicine, 2011 ; Korean Journal of Internal Medicine, 2013 ; UpToDate, 2019)
According to a study Role of neutrophil to lymphocyte and monocyte to lymphocyte ratios in the diagnosis of bacterial infection in patients with fever (Infection, 2017), high neutrophyl : lymphocyte ratio (NLR) and high monocyte : lymphocyte ratio (MLR) are much more common in bacterial than viral causes of fever:
In the present paper, we demonstrate that NLR and also MLR is higher
in patients hospitalized for fever due to bacterial infection, and
lower in those with viral infection, than in patients with
non-infectious causes of fever (Table 1).
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