The precipitin test in the diagnosis of tuberculosis

The precipitin test has been found to give reliable results in the diagnosis of active tuberculosis. The antigen is prepared by disrupting tubercle bacilli, preferable an old culture, with carbon dioxide by the method described by Larson, Hartzell and Diehl. 1 The disrupted bacteria are filtered through paper in order to remove the shells. The clear filtrate is layered over the serum to be tested, and the tubes incubated for a period up to two hours. A definite cloudy ring at the interface of the two fluids indicates a positive reaction. The cloud often appears within the first five minutes. In the far advanced cases, however, the reaction develops more slowly, but is usually very definite. Upon standing several hours the ring gradually becomes dispersed.

Thus far the blood serum of 190 cases have been examined. Of these, 100 were patients in the University Hospital and Dispensary, but not in the tubercular clinics. Ninety cases, representing all stages of tuberculosis, were from a local sanatorium. From the 100 cases not suspected of having tuberculosis, eleven positive reactions were obtained. Six of these have since been found to have evidence of tuberculosis. One died from hypertension, and at autopsy an active lesion was found in the apex of the right lung.

An interesting case was that of a newborn, whose mother was a far advanced case, giving a negative Von Pirquet but a positive precipitin test. The blood of the newborn gave a heavy precipitin reaction.

Of the 90 sanatorium cases 85 were positive and 5 negative. The 5 negative cases were either “healed” or “arrested.”

We have found that the acid fast actinomycetes, as A. gypsoides and A. asteroides, make a good antigens as the tubercle bacillus.