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When RCTs are consistent across a variety of
populations and settings, we should feel more
secure about the applicability of the
intervention. If it works in low risk and high
risk, young and old, East and West, it will
probably work in my patient. However, as Puliyel
and Sreenivas point out, RCTs don't always agree,
and sometimes diverge widely. When that happens,
we would like to know why. It could be any of the
PI...
When RCTs are consistent across a variety of
populations and settings, we should feel more
secure about the applicability of the
intervention. If it works in low risk and high
risk, young and old, East and West, it will
probably work in my patient. However, as Puliyel
and Sreenivas point out, RCTs don't always agree,
and sometimes diverge widely. When that happens,
we would like to know why. It could be any of the
PICO elements: the populations studied, the way
the intervention is delivered (dose, vehicle,
route, timing, etc), the comparator and
background treatments, or when or how the
outcomes were measured.[1] Or it can be that the
PICOs are the same, but that some of the trials
are flawed (poor randomisation, poor followup,
non-blinding, etc) and some not, leading to
confounding by trial quality. Systematic (and
unsystematic!) reviews should look for such
differences, and if they occur use them as an
opportunity to learn more about when and why a
treatment works or does not. However, that
requires considerable care to separate out the
possible true and artefactual causes of apparent disagreement between studies.
The Editors
References
[1] Glasziou PP, Sanders SL. Investigating causes
of heterogeneity in systematic reviews. Stat Med. 2002;21:1503-11.
In response to the Editor's invitation calling for short items on EBM related issues, we would like you to consider this statistical problem for possible publication.
The double-blind Randomised Controlled Trial (RCT) is the basis of
good evidence based medicine because it eliminates problems of bias and
confounding. However systematic reviews show different RCTs arriving at
diametrically op...
In response to the Editor's invitation calling for short items on EBM related issues, we would like you to consider this statistical problem for possible publication.
The double-blind Randomised Controlled Trial (RCT) is the basis of
good evidence based medicine because it eliminates problems of bias and
confounding. However systematic reviews show different RCTs arriving at
diametrically opposite conclusions. The reason for this is that the
samples for the RCTs are drawn from different populations and it reflects
the truth in those various populations. This matter is often overlooked
when met-analysis is done. When RCTs are aggregated in a meta-analysis we
have to aggregate the populations they represent – not the sample sizes.
Large samples from small populations will get undue weightage otherwise.
Meta-analysis as done presently can be misleading and unreliable.
I ran across your site concerning glucomine and sulphate knee cream. I took a cruise to Mexico and bought some cream there with glucomine and sulphate for 6.00. I am 65 and I have rheumatoid-osteoarthritis and am in pain
That cream worked for me but I cant find it anywhere here.
Can you help me find it please?
I read with optimism the note from Dr. Glasziou. It is encouraging to
know that systematic reviews on diagnostic tests are being considered as
part of national Cochrane movements. We badly need them. We have been
involved in this task ever since 1995 and published two systematic reviews
[1,2]. Quality of primary studies and methodological problems need to be
studied and new tools need to be developed....
I read with optimism the note from Dr. Glasziou. It is encouraging to
know that systematic reviews on diagnostic tests are being considered as
part of national Cochrane movements. We badly need them. We have been
involved in this task ever since 1995 and published two systematic reviews
[1,2]. Quality of primary studies and methodological problems need to be
studied and new tools need to be developed. Summary receiver operating
characteristics curve (sROC curve) is one method for pooling results of
primary studies. However, there are still many drawbacks that pooled sROC
curves can not tackle to date. The clinician needs to know the best
diagnostic test or clinical feature at different thresholds and in
different clinical scenarios. And sROC curves are not able to show them.
Pooled likelihood ratios (LRs) and diagnostic odds ratios (DORs) have been
proposed recently and seem attractive and quite easy to interpret for busy
practitioners [3]. Hopefully there will be an increasing number of
clinicians interested in translating the daily clinical problems into
answerable questions and trying the next brave step of trying to get their
own answers through the conduction of systematic reviews.
Evidence-based medicine has definitely influenced the practice of
medicine all over the world. Those of us teaching and practicing in
developing countries face several difficulties for testing whether EBM
works or not in our particular settings. Our patients are often poor and
have widely differing cultural backgrounds. We must adapt our discourse to
those characteristics. And this is a very difficult task to fulfill. But
our daily experience -pending to be systematically reported- strongly
suggests that it is not an impossible task.
Access to the medical literature used to be a nightmare for us.
Fortunately, we have now a substantial amount of full literature freely
available. Hinari must be commended for the reduction of this knowledge
gap between rich and poor nations. However, training in searching,
retrieving and most of all, critically appraising of the literature is
still in its infancy. We risk to be asphyxiated by all the published
studies if we do not develop systematic ways of recognizing the bad
literature from the good and relevant one. I wonder how far this pathway
has progressed in the way of a strong network involving clinicians and
researchers from developed and developing countries alike. Access to
Internet is still a pending problem. Free access to the medical literature
will be useless if medical students and physicians are charged with
expensive fees imposed by private companies that control access to
Internet, often in a monopoly way, like in Peru.
Finally, I was looking for some thoughts on the evidence base for
public health and health policy issues in Dr. Glaszious’s note, but found
nothing. Let’s hope that more systematic reviews on public health
interventions will become available. They are too scarce now. And this
evidence-based policy making will very likely need the discussion and
development of new standards in addition to systematic reviews of
randomized controlled trials [4]. Too many children are dying, almost all
in poor countries [5]. We have effective interventions for avoiding most
of these deaths [6] and it is immoral that they are not reaching those
that need them most. But in addition we need to study the effectiveness of
different delivery mechanisms of single effective interventions and on how
to strengthen health systems in the developing world [7]. Randomized
controlled trials are often not feasible or are unethical when we try to
know whether different delivery ways of public health interventions are
effective [4]. May I suggest the inclusion of this issue as part of the
scientific program of the 3rd International Conference of EBM Teachers?.
Will it be possible to put together EBM champions involved in the care of
individual patients with concerned public health researchers and policy
makers that are looking for more sound scientific base on which to make
decisions that will affect the lives of millions?. I invite you to take a
look at the Child Survival series and the Health Systems series published
in the Lancet in 2003 and 2004, respectively. They are a superb example of
ongoing efforts to construct an evidence-based health care at public
health level. We should build on those efforts.
References
1. Huicho L, Campos M, Rivera J, Guerrant RL. Fecal screening tests
in the approach to acute infectious diarrhea: a scientific overview.
Pediatr Infect Dis J 1996;15:486-94.
2. Huicho L, Campos-Sanchez M, Alamo C. Metaanalysis of urine screening
tests for determining the risk of urinary tract infection in children.
Pediatr Infect Dis J 2002;21:1-11.
3. Devillé WL, Buntinx F, Bouter LM, Montori VM, de Cet HCW, vander Windt
AWM, Bezemer PD. Conducting systematic reviews of diagnostic studies:
didactic guidelines. BMC Med Res Methodol 2002; 2: 9.
4. Victora CG, Habicht JP, Bryce J. Evidence-based public health: Moving
beyond randomized controlled trials. Am J Publ Health 2004;94:400-5.
5. Black RE, Morris SS, Bryce J. Where and why are 10 million children
dying every year?. Lancet 2003;361:2226-34.
6. Jones G, Steketee RW, Black RE, Bhutta ZA, Morris SS, and the Bellagio
Child Survival StudyGroup. How many child deaths can we prevent this year?
Lancet 2003; 362: 65–71.
7. Bryce J, el Arifeen S, Pariyo G, Lanata CF, Gwatkin D, Habicht JP, and
the
Multi-Country Evaluation of IMCI Study Group. Reducing child mortality:
can public health deliver? Lancet 2003; 362: 159–64.
I see many results in which potassium falls (a little) above the normal range.[1] I was wondering at what level I should be concerned about sudden death being the presenting symptom.
I reflected that the context in which the result was found affects my decision making.
A routine test which identifies a raised value, is less alarming than a test which is done for a reason, such as the presence of s...
I see many results in which potassium falls (a little) above the normal range.[1] I was wondering at what level I should be concerned about sudden death being the presenting symptom.
I reflected that the context in which the result was found affects my decision making.
A routine test which identifies a raised value, is less alarming than a test which is done for a reason, such as the presence of symptoms or perhaps because of a medication change.
This is analagous to the significance of a symptom or sign in the context of a focussed query versus routine enquiry (or screening).
One way of looking at it is in terms of the test characteristics of a diagnostic test versus a screening test. A screening test may have a higher cut point to increase specificity and reduce false positives. A diagnostic test may have a lower cut point to increase sensitivity and reduce false negatives.
Alternatively, looking at it as a Bayesian probability calculation, when doing the test for a reason (eliciting a symptom or sign for a reason) the prior probability (of a problem) is greater and hence one is influenced more even if the test (or symptom/sign) has a relatively small positive LR.
This is a very roundabout way of saying that if in doing routine annual bloods on a patient with hypertension treated with an ACE, I discovered a K of 6 say, I would perhaps feel this was not a cause for urgency. Conversely if someone presented with weakness and palpitations having recently commenced an ACE for diabetic nephropathy I might judge the same value of K to be more serious.
On the basis of this I would be interested to know what type of patients were included in the prognostic studies identified. Were they a broad selection of the population, such as seen in primary care, or were they perhaps patients more at risk of hyperkalemia, and its consequences, such as patients with diabetic nephropathy? Similarly, what was the context in which ECGs were related to potassium levels?
Reference
1. de Palma J R, Glasziou P. The first symptom of hyperkalaemia is death. Evid Based Med 2004; 9: 134-135
Shouldn't the RCT be done in such a way that the placebo also has
Camphor and peppermint oil in identical concentration to the actual cream?[1] It is already known that the latter two can have a good effect on osteoarthritis, especially in the elderly.
Reference
1. Reginster J-Y. A topical cream containing glucosamine and chondroitin sulphate reduced joint pain in osteoarthritis of...
Shouldn't the RCT be done in such a way that the placebo also has
Camphor and peppermint oil in identical concentration to the actual cream?[1] It is already known that the latter two can have a good effect on osteoarthritis, especially in the elderly.
Reference
1. Reginster J-Y. A topical cream containing glucosamine and chondroitin sulphate reduced joint pain in osteoarthritis of the knee. Evid Based Med 2003; 8: 154.
The paper in question has a strange problem: the definition of
cervicogenic headache. Reading the text, one must look to all headaches
that origins itself in cervical region, and there we have a conflict with
International Classification of Headaches: first described by Ottar
Sjaastad in late 1970s, the most correct assumption of cervicogenic headache
is a particular syndrome who origins the pain in C...
The paper in question has a strange problem: the definition of
cervicogenic headache. Reading the text, one must look to all headaches
that origins itself in cervical region, and there we have a conflict with
International Classification of Headaches: first described by Ottar
Sjaastad in late 1970s, the most correct assumption of cervicogenic headache
is a particular syndrome who origins the pain in C2 roots and have a
special pathopshisiology - this type of headache can also be classified
by indomethcacin-responsive headaches, and this fact is a dramatic one in
regard to the mechanisms envolved,particularly one certain pathway of
prostaglandins. Perhaps the cervicogenic headache has good results with
COX2 new drugs, but there are not therapeutics results with other
NSAIDs.The finest thing is the correct propedeutics of C2, the
neurological examination and not the ancillary ones.
At this paper results a doubt, at least, that the author is naming
cervicogenic headaches at all pain with some kind of relation with the
cervical spine, or the syndrome specially described and included in the
International Classification of Headaches: the last situation don’t have a
good chance to be analyzed…
Because of these facts, the results couldn’t be analyzed properly,
especially in view of evidence based medicine: we don’t know the nosology
of the cases presented.
The more appropriate approach to these is first the correct
nomination of the pain and, thus, the results of physical and/or
medication measures.
In a short resume, this paper does not fulfill the criteria to be
looked by the evidence medicine eyes.
In our primary care practice we are grappling with the diagnostic criteria for (type II) DM.
We use FPG as our main investigation with the WHO criteria of FPG <7.0 on two occasions defining diabetes.
In the event of repeated FPGs between 6 and 7 (& presumably a previous RPG 7-11.1) we have previously referred patients for an OGTT. However, we have found that this often does not lead to...
In our primary care practice we are grappling with the diagnostic criteria for (type II) DM.
We use FPG as our main investigation with the WHO criteria of FPG <7.0 on two occasions defining diabetes.
In the event of repeated FPGs between 6 and 7 (& presumably a previous RPG 7-11.1) we have previously referred patients for an OGTT. However, we have found that this often does not lead to a more definite diagnosis either.
Recently, we have considered using HBA1C as a second-line test in this group (RPG 6-7 x 2).
The local target HbA1C is 7.0.
Hence if HBA1C is < 7 we are reassured that such patients do not require medication and we offer lifestyle advice (and annual recall for re-testing).
In effect we are using FPG <7 (but >6) + HBA1C <7 to rule out diabetes, and this seems pragmatic since we would not wish to medicate this group unecessarily.
In the event that HBA1C is <7 we would presumably consider an OGTT or treat based on HBA1c alone (with metformin), this hasn't happened as yet.
This Cochrane review concluded that antibiotics reduce short to
medium-term persistence in children with persistent nasal discharge or
older children with radiographically confirmed sinusitis.
The EBM synopsis concluded that antibiotics are more effective than
placebo in children with persistent nasal discharge.
The 6 RCTs reviewed in the Cochrane review include four RCTs of older
ch...
This Cochrane review concluded that antibiotics reduce short to
medium-term persistence in children with persistent nasal discharge or
older children with radiographically confirmed sinusitis.
The EBM synopsis concluded that antibiotics are more effective than
placebo in children with persistent nasal discharge.
The 6 RCTs reviewed in the Cochrane review include four RCTs of older
children with radiographically confirmed sinusitis and two RCTs of children
with peristent nasal discharege (and no radiographic inclusion criteria).
The four RCTs with radiographic inclusion criteria found a benefit for
antibiotics.
Of the two RCTs of children with persistent symptoms (without
radiographic evaluation, i.e. the more common presentation in practice),
one had 188 patients and the other had only 13 patients. The RCT with 188
patients did not find any benefit for antibiotics, despite being funded by
the pharmaceutical company.
The data suggest that antibiotics would be helpful in children with
radiographically confirmed sinusitis (although this is not sufficient data
to show that radiogrpahic studies are warranted to find this subgroup),
BUT antibiotics for unselected children with persistent sinusitis symptoms
are not effective.
For those who like analogies, apples (representing studies of
children with persistent symptoms) were found to be rotten, while oranges
(representing studies of children with radiographic sinusitis) were found
to be healthy.
The Cochrane review combined apples and oranges. Since oranges
outnumbered apples more than two to one, the overall conclusion was
favorable and found that apples and oranges are healthy--without making
separate conclusions.
The EBM summary concluded that apples are healthy. However, the data still suggests that apples are rotten and oranges are
healthy.
I found this article interesting on the debate whether the benfit of
wearing elasticated stockings on long haul flights were useful in
prevention of DVT's in passengers. As you questioned the small amount used
in the study were not significant therefore inconclusive on
recommendations.
I was wondering how the staff, namely the pilots cope who make more
regular long haul flights than the passeng...
I found this article interesting on the debate whether the benfit of
wearing elasticated stockings on long haul flights were useful in
prevention of DVT's in passengers. As you questioned the small amount used
in the study were not significant therefore inconclusive on
recommendations.
I was wondering how the staff, namely the pilots cope who make more
regular long haul flights than the passengers . How do they prevent the
risks of DVT's. As we don't read about them in the press unlike if a
passenger aquires a DVT.
When RCTs are consistent across a variety of populations and settings, we should feel more secure about the applicability of the intervention. If it works in low risk and high risk, young and old, East and West, it will probably work in my patient. However, as Puliyel and Sreenivas point out, RCTs don't always agree, and sometimes diverge widely. When that happens, we would like to know why. It could be any of the PI...
Dear Editor,
In response to the Editor's invitation calling for short items on EBM related issues, we would like you to consider this statistical problem for possible publication.
The double-blind Randomised Controlled Trial (RCT) is the basis of good evidence based medicine because it eliminates problems of bias and confounding. However systematic reviews show different RCTs arriving at diametrically op...
I ran across your site concerning glucomine and sulphate knee cream. I took a cruise to Mexico and bought some cream there with glucomine and sulphate for 6.00. I am 65 and I have rheumatoid-osteoarthritis and am in pain
That cream worked for me but I cant find it anywhere here. Can you help me find it please?
Thank you,
Peggy
Dear Editor,
I read with optimism the note from Dr. Glasziou. It is encouraging to know that systematic reviews on diagnostic tests are being considered as part of national Cochrane movements. We badly need them. We have been involved in this task ever since 1995 and published two systematic reviews [1,2]. Quality of primary studies and methodological problems need to be studied and new tools need to be developed....
I see many results in which potassium falls (a little) above the normal range.[1] I was wondering at what level I should be concerned about sudden death being the presenting symptom.
I reflected that the context in which the result was found affects my decision making.
A routine test which identifies a raised value, is less alarming than a test which is done for a reason, such as the presence of s...
Dear Editor
Shouldn't the RCT be done in such a way that the placebo also has Camphor and peppermint oil in identical concentration to the actual cream?[1] It is already known that the latter two can have a good effect on osteoarthritis, especially in the elderly.
Reference
1. Reginster J-Y. A topical cream containing glucosamine and chondroitin sulphate reduced joint pain in osteoarthritis of...
Dear Editor
The paper in question has a strange problem: the definition of cervicogenic headache. Reading the text, one must look to all headaches that origins itself in cervical region, and there we have a conflict with International Classification of Headaches: first described by Ottar Sjaastad in late 1970s, the most correct assumption of cervicogenic headache is a particular syndrome who origins the pain in C...
Dear Editor
In our primary care practice we are grappling with the diagnostic criteria for (type II) DM.
We use FPG as our main investigation with the WHO criteria of FPG <7.0 on two occasions defining diabetes.
In the event of repeated FPGs between 6 and 7 (& presumably a previous RPG 7-11.1) we have previously referred patients for an OGTT. However, we have found that this often does not lead to...
Dear Editors
This Cochrane review concluded that antibiotics reduce short to medium-term persistence in children with persistent nasal discharge or older children with radiographically confirmed sinusitis.
The EBM synopsis concluded that antibiotics are more effective than placebo in children with persistent nasal discharge.
The 6 RCTs reviewed in the Cochrane review include four RCTs of older ch...
Dear Editor
I found this article interesting on the debate whether the benfit of wearing elasticated stockings on long haul flights were useful in prevention of DVT's in passengers. As you questioned the small amount used in the study were not significant therefore inconclusive on recommendations.
I was wondering how the staff, namely the pilots cope who make more regular long haul flights than the passeng...
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