304 LETTERS Comment on the article by Breedveld et al To the Editor: The article by Breedveld et al on the use of magnetic resonance imaging (MRI) in patients with rheumatoid arthritis and subluxations of the cervical spine (Breedveld FC, Algra PR, Vielvoye CJ, Cats A: Magnetic resonance imaging in the evaluation of patients with rheumatoid arthritis and subluxations of the cervical spine. Arthritis Rheum 30:624- 629, 1987) was extremely informative. I would add that, if the presence or absence of neurologic signs as possible evidence of cord or central nervous system involvement is considered the “gold standard,” it would be of value to estimate the sensitivity and specificity of the MRI. Analysis of the data presented by Breedveld and coworkers reveals that the sensitivity of MRI was 75% if only patients in neurologic class 111 are included, and 66% if patients in classes I1 and 111, according to their classification, are included. The specificity is 77% if only patients in class I11 are included, but it increases to 89% when both class I1 and 111 patients are included (see Table 1). The overall predictive value for MRI is 76% in both cases. Therefore, since neither the sensitivity, the specificity, nor the overall predictive value of MRI appears to be extremely high (compared with the presence or absence of neurologic signs), the value of MRI in the assessment of Table 1. Sensitivity and specificity of magnetic resonance imaging (MRI) in the evaluation of patients with rheumatoid arthritis and cervical spine involvement* Neurologic signs (classes I1 and Ill) MRI result Present Absent Total Abnormal 8 I 9 Normal 4 8 12 Total 12 9 21 * The data result in a sensitivity of 66%, a specificity of 89%, and an overall predictive value of 76% for MRI. rheumatoid arthritis patients with cervical spine involvement remains to be determined. That determination can be facili- tated by prospectively following a cohort of patients and recording their MRI and neurologic sign data in the 4 cells of a 2 x 2 table (see Table I). It may well be that MRI would, in the not-too-distant future, become the “gold standard” to define cervical spine involvement in rheumatoid arthritis. Graciela S. Alarcon, MD, MPH The University of Alabama at Birmingham Birmingham, AL

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304 LETTERS

Comment on the article by Breedveld et al To the Editor:

The article by Breedveld et al on the use of magnetic resonance imaging (MRI) in patients with rheumatoid arthritis and subluxations of the cervical spine (Breedveld FC, Algra PR, Vielvoye CJ, Cats A: Magnetic resonance imaging in the evaluation of patients with rheumatoid arthritis and subluxations of the cervical spine. Arthritis Rheum 30:624- 629, 1987) was extremely informative. I would add that, if the presence or absence of neurologic signs as possible evidence of cord or central nervous system involvement is considered the “gold standard,” it would be of value to estimate the sensitivity and specificity of the MRI.

Analysis of the data presented by Breedveld and coworkers reveals that the sensitivity of MRI was 75% if only patients in neurologic class 111 are included, and 66% if patients in classes I1 and 111, according to their classification, are included. The specificity is 77% if only patients in class I11 are included, but it increases to 89% when both class I1 and 111 patients are included (see Table 1 ) . The overall predictive value for MRI is 76% in both cases.

Therefore, since neither the sensitivity, the specificity, nor the overall predictive value of MRI appears to be extremely high (compared with the presence or absence of neurologic signs), the value of MRI in the assessment of

Table 1. Sensitivity and specificity of magnetic resonance imaging (MRI) in the evaluation of patients with rheumatoid arthritis and cervical spine involvement*

Neurologic signs (classes I1 and Ill)

MRI result Present Absent Total

Abnormal 8 I 9 Normal 4 8 12 Total 12 9 21

* The data result in a sensitivity of 66%, a specificity of 89%, and an overall predictive value of 76% for MRI.

rheumatoid arthritis patients with cervical spine involvement remains to be determined. That determination can be facili- tated by prospectively following a cohort of patients and recording their MRI and neurologic sign data in the 4 cells of a 2 x 2 table (see Table I ) . It may well be that MRI would, in the not-too-distant future, become the “gold standard” to define cervical spine involvement in rheumatoid arthritis.

Graciela S. Alarcon, MD, MPH The University of Alabama at Birmingham Birmingham, AL