Cold Hemagglutination in Primary Atypical Pneumonia and Other Common Infections

Recent reports indicate that large amounts of a cold hemagglutinin appear frequently in the blood of patients with primary atypical pneumonia.1Apparently, this is not true of patients with other common infections of the respiratory tract, such as pneumococcic pneumonia, the common cold, influenza and pulmonary tuberculosis.2In view of the simplicity of the titration of cold agglutinin in the serum, this procedure promises to be of value as a practical aid in the differentiation of primary atypical pneumonia from the other common types of pneumonia. This differentiation is often difficult, since no clinical or laboratory finding is characteristic of the former syndrome.3 During the winter and spring of 1943-1944, we studied the phemonemon of cold hemagglutination in 115 patients with pneumonia, in 257 patients with other infections and in 100 normal hospital personnel. This was done to evaluate further the specificity and significance of high titers