We thank Dr. Nicholson and Prof. Cullinan for their interest in our
paper,[1] and welcome the opportunity to respond to their comments and
provide clarification.
We did review the most up-to-date version of all guidelines,
including the 2010 version of the BOHRF guidelines. In the "Results"
section of our paper, the first column of Table 1 cites the most recent
guideline versions published in the peer-reviewed...
We thank Dr. Nicholson and Prof. Cullinan for their interest in our
paper,[1] and welcome the opportunity to respond to their comments and
provide clarification.
We did review the most up-to-date version of all guidelines,
including the 2010 version of the BOHRF guidelines. In the "Results"
section of our paper, the first column of Table 1 cites the most recent
guideline versions published in the peer-reviewed literature; for the
BOHRF guidelines that was a summary of the 2004 version, published in
2005.[2] Unsurprisingly, our focus was indeed on the 2010 evidence review
and recommendations document,[3] which we appropriately cite in the second
column of Table 1 and not only in the "Introduction" section, as
suggested. It is not clear to us why Nicholson and Cullinan thought that
we appraised the older version and not the latest one.
As explained in the "Methods" section of our paper, for every
guideline reviewed "we thoroughly searched for any accompanying technical
and supporting documents in order to better inform our assessments".
Accordingly, we did of course visit the BOHRF website and were very much
aware of the documents that Nicholson and Cullinan make reference to.
However, these are short informational brochures based on the BOHRF
guidelines, whereas the ERS document is much more comprehensive; it
summarizes all key questions and recommendations along with the associated
evidence grades, and is suitably titled as "pocket guidelines".[4]
Consequently, the statement in our paper that "ERS was the only guideline
that provided a pocket version" cannot, in our opinion, be reasonably
described as "factually incorrect".
In the AGREE II, the existence of summary documents represents only
one criterion of a single item (out of four) in the "Applicability"
domain. In any event though, since all appraisers were indeed aware and
took account of the BOHRF brochures, neither the score for "Applicability"
nor the overall score of the BOHRF guidelines is "incorrect and
unreliable" as suggested.
Having said that, it should be pointed out that the AGREE II does not
claim to be a perfectly objective and repeatable instrument, even though
the high number of appraisers in our review ensures improved reliability.
The AGREE II does require a measure of personal judgement, and as its
authors note, "the criteria and considerations [outlined] are there to
guide, not replace, these judgements".[5] It assesses a strictly defined
aspect of guideline quality, and does not evaluate, for example, the
clinical appropriateness or validity of the recommendations themselves.[6]
Therefore, appraisals using the AGREE II should not be perceived as
passing judgement on the work of guideline developers, and are best used
as tools to identify areas for further improvement.
We do acknowledge the mistaken URL in reference 9 of our paper, and
thank Nicholson and Cullinan for pointing this out. The correct URL is
http://www.bohrf.org.uk/downloads/OccupationalAsthmaEvidenceReview-
Mar2010.pdf.
1 Lytras T, Bonovas S, Chronis C, et al. Occupational Asthma
guidelines: a systematic quality appraisal using the AGREE II instrument.
Occup Environ Med 2014;71:81-6. doi:10.1136/oemed-2013-101656
2 Nicholson PJ, Cullinan P, Taylor AJN, et al. Evidence based
guidelines for the prevention, identification, and management of
occupational asthma. Occup Environ Med 2005;62:290-9.
doi:10.1136/oem.2004.016287
3 Nicholson PJ, Cullinan P, Burge PS, et al. Occupational asthma:
Prevention, identification & management: Systematic review &
recommendations. London: : British Occupational Health Research Foundation
2010. http://www.bohrf.org.uk/downloads/OccupationalAsthmaEvidenceReview-
Mar2010.pdf
4 European Respiratory Society. ERS Pocket Guidelines. Work-related
Asthma: Guidelines for the Management of Work-related Asthma. European
Respiratory Society 2012. http://www.ers-
education.org/Media/Media.aspx?idMedia=208120
5 AGREE Next Steps Consortium. The AGREE II instrument. 2009.
http://www.agreetrust.org/index.aspx?o=1397
6 Brouwers MC, Kho ME, Browman GP, et al. AGREE II: advancing
guideline development, reporting and evaluation in health care. CMAJ
2010;182:E839-842. doi:10.1503/cmaj.090449
We write to correct errors in the paper Occupational asthma
guidelines: a systematic quality appraisal using the AGREE II instrument
1.
The methodology for this study states that the authors reviewed the
most up to date versions of guidelines. While in their Introduction the
authors cite (their reference 9) a statement from the 2010 BOHRF
systematic review 2; within the Results section it is clear that they
a...
We write to correct errors in the paper Occupational asthma
guidelines: a systematic quality appraisal using the AGREE II instrument
1.
The methodology for this study states that the authors reviewed the
most up to date versions of guidelines. While in their Introduction the
authors cite (their reference 9) a statement from the 2010 BOHRF
systematic review 2; within the Results section it is clear that they
appraised their reference 35 which is a short version of the 2004 BOHRF
systematic review 3 published in Occup Environ Med in 2005 4.
The authors state that only the European Respiratory Society
guidelines produced pocket sized versions. This is factually incorrect.
Both the 2004 and 2010 BORF reviews published a series of concise
summaries for: a) employers, workers and their representatives, b) general
practitioners (GPs) and practice-based nurses, c) occupational health
professionals; and d) an algorithm for GPs. All are freely accessible at
http://www.bohrf.org.uk/projects/asthma.html. Consequently the authors
scored the BOHRF guidelines incorrectly low for domain 5 (applicability);
as a result the overall quality score is incorrect and unreliable.
Within the reference section the authors' hyperlink to the 2010 BOHRF
occupational asthma review is incorrect; it actually being a link to a
review of occupational contact dermatitis.
1. Lytras T, Bonovas S, Chronis C, et al. Occupational Asthma
guidelines: a systematic quality appraisal using the AGREE II instrument.
Occup Environ Med. 2014;71:81-6.
2. Nicholson PJ, Cullinan P, Burge PS, et al. Occupational asthma:
Prevention, identification & management: Systematic review &
recommendations. London: British Occupational Health Research Foundation,
2010.
3. Nicholson PJ, Cullinan P, Newman Taylor AJ, et al. Evidence based
guidelines for the prevention, identification, and management of
occupational asthma. Occup Environ Med 2005;62:290-9.
4. Newman Taylor AJ, Nicholson PJ, Cullinan P, et al. Occupational
asthma: Prevention, identification & management: Systematic review
& recommendations. London: British Occupational Health Research
Foundation, 2004.
Conflict of Interest:
Authors of BOHRF guidelines reviewed in this paper.
We thank Dr. Morfeld for his comments on our updated mortality study
of the U.S. coal miners study.[1] However, we disagree with his assertion
that the excess of lung cancer we observed must be attributed to smoking
alone. Firstly, despite the smoking prevalence being higher in our cohort
than in the U.S. population in 1970, smokers in our population were
significantly less likely to be heavy smokers (> 24 cigarettes...
We thank Dr. Morfeld for his comments on our updated mortality study
of the U.S. coal miners study.[1] However, we disagree with his assertion
that the excess of lung cancer we observed must be attributed to smoking
alone. Firstly, despite the smoking prevalence being higher in our cohort
than in the U.S. population in 1970, smokers in our population were
significantly less likely to be heavy smokers (> 24 cigarettes daily)
than men in the general US population (12.4% vs. 28.0%). Secondly, greater
weight should be given to the findings from the internal analysis, which
controlled for smoking, than to the SMR analysis. Here, as Dr. Morfeld
acknowledges, there was a clear dose-response relationship between coal-
mine dust exposure and lung cancer. Of note, there was an inverse
relationship between radiographic CWP status and lung cancer mortality,
implying that CWP and lung cancer were competing causes of death, and
leading to weakening of the relationship between dust exposure and lung
cancer for the older miners (i.e., those exposed to the high levels of
dust existing prior to the 1969 Federal dust regulations).
Table 1 shows the mean cumulative coal dust exposures by year, as
requested by Dr. Morfeld. These levels were lower in the last eight years
of follow-up and were higher among lung cancer cases than among all
subjects in that decade. This is probably explained by the fact that
subjects with higher cumulative exposures were more likely to die during
the earlier years of follow-up due to the effects of exposure and their
age.
Dr. Morfeld correctly stated that we lacked work histories on our
miners after enrolment (1969 to 1971), but incorrectly asserted that work
histories were absent before enrolment. The lack of work histories in the
post-enrolment period may have introduced some misclassification of
exposures. However, as we and others have emphasized,[2,3] and as
demonstrated by our sensitivity analysis, any such misclassification is
likely minimal as most participants accumulated the bulk of their exposure
before enrolment.
We agree with Dr. Morfeld, and stated in our article, that the
British study of coal miners [4] had better exposure data than our study.
While both studies show an excess of lung cancer in their most recent
period of follow-up, [1,4] the British findings suggest that the excess is
most strongly associated with silica, rather than with coal dust exposure
as seen in our study. However, from both studies it is clear that there
is an excess of lung cancer among coal miners which is unlikely explained
by smoking alone.
Finally, we are confused by Dr. Morfeld's reference to the healthy
worker survivor effect as a reason for dismissing our findings. As has
been shown [3] the study was subject to a strong healthy worker survivor
effect, causing a reduction in mortality in the early years of follow-up.
We remain firm in our conclusion that "Our findings and those from
the British coal-miners cohort strongly suggest the need for continued
investigation of lung cancer mortality and incidence among coal
miners."[1]
Table I: Coal mine dust by year of death among all cohort members and
among those for whom the underlying cause of death was lung cancer
Mean Cumulative Exposure
Coal Mine Dust
(mg/m3-yrs)
All Lung Cancer
(n= 8,829) (n= 568)
Calendar
year of death
1970-1989 89.7 86.9
1980-1999 82.0 75.5
2000-2007 42.8 51.5
Literature
1. Graber, J.M., Stayner, L.T., Cohen,R.A., Conroy, L.M., Attfield,
M. D., Respiratory disease mortality among US coal miners; results after
37 years of follow-up. Occup Environ Med, 2014. 71: p. 30-39.
2. Kuempel, E.D., et al., Exposure-response analysis of mortality among
coal miners in the United States. Am J Ind Med, 1995. 28(2): p. 167-84.
3. Attfield, M.D. and E.D. Kuempel, Mortality among U.S. underground coal
miners: a 23-year follow-up. Am J Ind Med, 2008. 51(4): p. 231-45
4. Miller, B.G. and L. MacCalman, Cause-specific mortality in British coal
workers and exposure to respirable dust and quartz. Occup Environ Med,
2010. 67(4): p. 270-6
I read with interest about the updated US coalminer mortality
study[1]. The lung cancer SMR was slightly elevated (SMR=1.08, 95% CI:
1.00-1.18). This excess is unexceptionable because of a higher proportion
of smokers at the start of follow-up in 1969/1971 (current smokers: 54%)
in comparison to the US male population in 1970 (44.1%). Internal analyses
showed an association of lung cancer mortality...
I read with interest about the updated US coalminer mortality
study[1]. The lung cancer SMR was slightly elevated (SMR=1.08, 95% CI:
1.00-1.18). This excess is unexceptionable because of a higher proportion
of smokers at the start of follow-up in 1969/1971 (current smokers: 54%)
in comparison to the US male population in 1970 (44.1%). Internal analyses
showed an association of lung cancer mortality with coalmine dust exposure
but only during the last follow-up interval from 2000 to 2007. Thus, it is
of interest to see the distribution of the cumulative exposures across the
different calendar time periods. It remains unclear why this information
was not given in Table 2 (why does Table 2 report on 568 lung cancer cases
but Table 4 on 583 cases?)
This US study suffers from an incomplete assessment of occupational
histories in coalminers: no start and end date of jobs held before
1969/1971 available, no information on jobs held after 1969/1971, and no
end date of working as a coalminer for 16.2% of cohort members. Thus, only
a crude assessment of exposure to coalmine dust up to the start of follow-
up was possible: no time-dependent exposure analysis or lagging of
exposures could be done. Crystalline silica concentration data suffered
from additional limitations because measurements were available only after
1981 but had to be allocated to jobs held before 1969/1971.
The largest study to date with better assessment of exposures in a
time-dependent manner was performed in the UK[2]: the overall evidence
does not support a lung cancer excess risk due to coalmine dust exposure.
The findings of the US study do not seem to change this view despite
obvious limitations due to the Healthy Worker Survivor Effect (models that
adjust for time since last employment do not solve this problem)[3].
References
1 Graber JM, Stayner LT, Cohen RA, et al. Respiratory disease
mortality among US coal miners; results after 37 years of follow-up. Occup
Environ Med 2014;71:30-39.
2 Miller BG, MacCalman L. Cause-specific mortality in British coal
workers and exposure to respirable dust and quartz. Occup Environ Med
2010; 67:270-276.
3 Naimi AI, Richardson DB, Cole SR. Causal Inference in Occupational
Epidemiology: Accounting for the Healthy Worker Effect by Using Structural
Nested Models. Am J Epidemiol. 2013;178:1681-1686.
Conflict of Interest:
Yes, I have a competing interest.
The author performed epidemiological studies on German coalminers and gives scientific advice to the German coalmining industry.
We thank Dr. Nicholson and Prof. Cullinan for their interest in our paper,[1] and welcome the opportunity to respond to their comments and provide clarification.
We did review the most up-to-date version of all guidelines, including the 2010 version of the BOHRF guidelines. In the "Results" section of our paper, the first column of Table 1 cites the most recent guideline versions published in the peer-reviewed...
We write to correct errors in the paper Occupational asthma guidelines: a systematic quality appraisal using the AGREE II instrument 1.
The methodology for this study states that the authors reviewed the most up to date versions of guidelines. While in their Introduction the authors cite (their reference 9) a statement from the 2010 BOHRF systematic review 2; within the Results section it is clear that they a...
We thank Dr. Morfeld for his comments on our updated mortality study of the U.S. coal miners study.[1] However, we disagree with his assertion that the excess of lung cancer we observed must be attributed to smoking alone. Firstly, despite the smoking prevalence being higher in our cohort than in the U.S. population in 1970, smokers in our population were significantly less likely to be heavy smokers (> 24 cigarettes...
Dear Editor,
I read with interest about the updated US coalminer mortality study[1]. The lung cancer SMR was slightly elevated (SMR=1.08, 95% CI: 1.00-1.18). This excess is unexceptionable because of a higher proportion of smokers at the start of follow-up in 1969/1971 (current smokers: 54%) in comparison to the US male population in 1970 (44.1%). Internal analyses showed an association of lung cancer mortality...