To The Editor:
In the paper "Magnetic Resonance Imaging of the Knee in Children and
Adolescents. Its Role in Clinical Decision-Making"
(2005;87:497-502), Luhmann et
al. proved that arthroscopic findings were better correlated with the
orthopaedic surgeon's diagnosis based on clinical examination, plain
radiographs, and magnetic resonance imaging than with the interpretation of
magnetic resonance images by a group of radiologists. Because of
methodological flaws, I do not think that we can extend this conclusion to
orthopaedic surgeons and radiologists in general. The reasons are as
follows.
First, comparison of two groups' performances should be performed by a
third party or at least by an investigator who is not directly involved in the
data collection. The orthopaedic surgeon involved in the clinical evaluation
was the first author of this paper, and the radiologists probably consisted of
pediatric radiologists with different amounts of expertise in these knee
disorders.
Second, the radiologists had access to plain radiographs and the
orthopaedic surgeon's presumptive diagnosis. It was uncertain whether the
results of the clinical assessment and the level of confidence in the
diagnosis were available to the radiologists. Radiologists' evaluations of
imaging studies are based on trust in the referring physician's clinical
assessments, and radiologists can be easily misled if the referring
physician's assessment is inadequate or inaccurate. Without close
communication and feedback, the radiologists' interpretations lose accuracy,
since there are substantial overlaps of normal and borderline abnormalities in
many circumstances.
Third, the authors included "probable" and
"possible" diagnoses as positive diagnoses without establishing
consensus in the confidence level. The possible diagnosis may have been made
only to raise a suspicion even if the possibility was considered to be
small.
Fourth, the orthopaedic surgeon knew the findings of the magnetic resonance
imaging done outside the institution at the initial assessment of forty-one of
the ninety-six patients. Thus, in nearly half of the cases, the clinical
assessment included magnetic resonance imaging findings.
I believe that, because of these methodological flaws, the conclusion of
this paper should not be extended to clinical practice in other settings. In
addition, the opinion of the radiologists is not included in this paper, and
the statements appear one-sided.
Dr. Ehara raises several issues, which I will discuss separately.
The issue of the method of data collection is raised. As stated in the
paper, the radiologists' preoperative interpretation of the magnetic resonance
imaging and the surgeon's preoperative diagnosis were documented prior to the
arthroscopic surgery. Dr. Ehara points to potential bias in the data
collection that may have altered the findings of the study. Data analysis was
performed by an experienced medical statistician, who obviously was not
involved in the care of the patients.This study replicated "real world" clinical medicine.
Radiologists at outside imaging centers who are interpreting magnetic
resonance imaging scans ordered by physicians often have little or no
information about the clinical diagnosis (and typically do not have any plain
radiographs, as these are at another facility). This is especially true when
the scans were ordered by primary care physicians.The terms "probable" and "possible" were found only
on the radiologists' formal interpretations of the magnetic resonance imaging.
The surgeon's preoperative diagnosis was always that the problem was or was
not present. This issue of how to treat the "probable" and
"possible" diagnoses based on the magnetic resonance imaging was
discussed with the other authors of the manuscript. There was a consensus that
we should include these as positive findings since primary caregivers and
patients treat them as "real" diagnoses; hence, they drive patient
referrals to the orthopaedic surgeon's office. It is at that point that the
onus of responsibility is on the orthopaedic surgeon to rule out the finding
as a real problem, since primary caregivers, families, patients, and insurance
companies think that magnetic resonance imaging is the "gold
standard" for definitive diagnosis of knee disorders.I refer Dr. Ehara to the Methods section of our paper. All preoperative
diagnoses made by the clinical surgeon were recorded after a history was
recorded, a physical examination was performed, and the plain radiographs and
the magnetic resonance imaging scan (and the interpretation of the scan) were
reviewed, regardless of where the magnetic resonance imaging was
performed.
The issue of the method of data collection is raised. As stated in the
paper, the radiologists' preoperative interpretation of the magnetic resonance
imaging and the surgeon's preoperative diagnosis were documented prior to the
arthroscopic surgery. Dr. Ehara points to potential bias in the data
collection that may have altered the findings of the study. Data analysis was
performed by an experienced medical statistician, who obviously was not
involved in the care of the patients.
This study replicated "real world" clinical medicine.
Radiologists at outside imaging centers who are interpreting magnetic
resonance imaging scans ordered by physicians often have little or no
information about the clinical diagnosis (and typically do not have any plain
radiographs, as these are at another facility). This is especially true when
the scans were ordered by primary care physicians.
The terms "probable" and "possible" were found only
on the radiologists' formal interpretations of the magnetic resonance imaging.
The surgeon's preoperative diagnosis was always that the problem was or was
not present. This issue of how to treat the "probable" and
"possible" diagnoses based on the magnetic resonance imaging was
discussed with the other authors of the manuscript. There was a consensus that
we should include these as positive findings since primary caregivers and
patients treat them as "real" diagnoses; hence, they drive patient
referrals to the orthopaedic surgeon's office. It is at that point that the
onus of responsibility is on the orthopaedic surgeon to rule out the finding
as a real problem, since primary caregivers, families, patients, and insurance
companies think that magnetic resonance imaging is the "gold
standard" for definitive diagnosis of knee disorders.
I refer Dr. Ehara to the Methods section of our paper. All preoperative
diagnoses made by the clinical surgeon were recorded after a history was
recorded, a physical examination was performed, and the plain radiographs and
the magnetic resonance imaging scan (and the interpretation of the scan) were
reviewed, regardless of where the magnetic resonance imaging was
performed.
Dr. Ehara raises concern about the ability to generalize the findings of
this study to clinical medicine. Our study demonstrated that the orthopaedic
surgeon should personally review all magnetic resonance imaging scans and not
rely on the radiologist's interpretation. Extrapolating the findings of any
study beyond the study purposes should always be done with extreme
caution.