Did read your commentary and the French paper (Gendrel et al). Looks
promising indeed. BTW, you have a very educational site and I enjoy reading
W.r.t to the paper, I had 3 concerns:
1. As you stated, to be really useful, any test has to be applied to the
relevant study population (ED), i.e. when they present with fever and are
relatively well looking. Then, one would like to have a screening test for
bacteremia/potential SBI, with high sensitivity and good PPV (those who have
the disease amongst those with a positive test) . This would help decide
which ones need antibiotics.
There is significant "sampling bias" in this study population. It includes
all patients who were febrile and were sick enough to warrant admission, as
deemed by the ED staff. Therefore, patients would be more likely to have an
abnormal test because they are sicker (shock, meningitis etc) This would
tend to overestimate the sensitivity.
2. Their PPV was calculated based on a prevalence of bacterial infection of
25% and 50%. In reality, this prevalence is lower, hence most screening
tests for OB/SBI tend to have lower PPV's.
3. Their age range was broad.(1 month to 15 years). I would have preferred
if they had provided the ROC curves for the younger age group who are at
risk for occult bacterial infections..i.e. where clinical exam is not
discriminatory. Personally, I expect a 7 yr. old say to provide clinical
clues of invasive or non invasive bacterial infection versus viral
illnesses. I really don't need a lab. test in that age group to make that
I liked many things about the paper:
1. Their attempt at confirming viral illnesses with PCR for enteroviral
2. What looked really promising was that, in non infectious inflammatory
conditions, like JRA, KD etc the level of < 2 was discriminatory. This is
unlike many other markers that we have.
3. PCT is relatively easy and inexpensive to assay.
4. It has shown promise in sepsis states from the adult literature.
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