To the Editor.—
In their article on acute hemolytic anemia with Mycoplasma pneumoniae pneumonia (236: 1140, 1976), Drs Turtzo and Ghatak mention that the diagnosis of M pneumoniae infection is usually made on the basis of a rising titer of cold agglutinin (CA). They acknowledge the fact that the CA test is unspecific, since other infections (eg, those caused by virus) may give a positive CA titer. However, their statement that titers in these cases are usually low (1:32 or less) in contrast to CA titers in M pneumoniae infections is not documented and is in disagreement with other findings.1Their miscitation of an article2 by saying that a fourfold rise in CA titer is virtually diagnostic creates a pitfall for the clinician, since CA titer rises of the same magnitude may, in fact, be seen during infections other than those caused by M pneumoniae.1The authors
Lind K. Diagnosis of Mycoplasma pneumoniae Infection. JAMA. 1977;237(18):1929–1930. doi:10.1001/jama.1977.03270450019008
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