Searles and McKendry developed criteria for the diagnosis of methotrexate-induced pneumonitis in patients with rheumatoid arthritis. The authors are from the University of Ottawa.
Diagnostic features:
(1) acute onset of shortness of breath
(2) fever > 38°C
(3) tachypnea >= 28 breaths per minute AND nonproductive cough
(4) pulmonary interstitial or alveolar infiltrates on chest X-ray
(5) WBC count <= 15,000 per µL (with or without eosinophilia)
(6) negative blood and sputum cultures for pathogenic organisms
(7) pulmonary function tests show a restrictive pattern with decreased diffusion capacity
(8) PaO2 < 55 mm Hg on room air at time of admission (or initial evaluation)
(9) histopathology shows:
(9a) (bronchiolitis) OR (interstitial pneumonitis with giant cells) AND
(9b) no pathogenic microorganisms
where:
• Feature 6 (negative cultures) is an obligatory feature for diagnosis.
Total Number of Features Present
Diagnostic Feature #6
Interpretation
>= 6
met
definite
5
met
probable
4
met
possible
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