This article deals with the question of the accuracy of serologic tests of spinal fluids that are tinged with blood. Any one who has performed many lumbar punctures has had his share of "bloody taps." All of us, no doubt, have frequently questioned the reliability of the report from the laboratory on serologic reactions in such cases. In our own clinic the occasional lack of agreement of serologic reactions with some of the clinical findings as well as the occasional lack of uniformity of the reactions to the Kahn test of the cerebrospinal fluid from week to week has led us to investigate this matter more thoroughly.
Kafka1 was one of the first to emphasize the importance of contamination of the spinal fluid with blood. He advised that the amount of blood in the specimen be estimated and added to a known normal cerebrospinal fluid, and the result noted.
LOVEMAN AB, STOCKING L. KAHN REACTION WITH SPINAL FLUIDS CONTAINING VARYING AMOUNTS OF SYPHILITIC BLOOD. Arch Derm Syphilol. 1934;29(5):653–657. doi:10.1001/archderm.1934.01460110011002