In a previous communication1 the routine use of the Laughlen test2 for syphilis in blood donors was described. The test was observed to be of value as an exclusion test, provided that the serum was inactivated prior to use, but a sufficient number of false positive results were obtained to indicate that the test might not be suitable as a diagnostic procedure. The present extended investigation of the Laughlen test deals with the thermal conditions necessary for the satisfactory inactivation of serum and a study of the accuracy of the test in the presence of various clinical conditions.
The preliminary work referred to was concerned with the value of the Laughlen test with (a) fresh unheated serum, (b) stored serum and (c) inactivated serum. In 10 per cent of the fresh unheated serums from syphilitic persons the reaction was negative, but the same serums stored for several days