In a review1 of 4,595 Friedman tests performed by twenty-six different clinical pathologists, it was shown that 5.1 per cent of the tests were false negatives and 0.95 per cent were false positives. In ectopic pregnancy 77.8 per cent were correct positives and 22.2 per cent were incorrect negatives. The technic employed in this series consisted of the injection of 10 cc. of urine into one nonpregnant mature female rabbit followed by gross inspection of the ovaries forty-eight hours later.
At Mount Sinai Hospital, 1,137 Friedman tests have been performed to date. The technic employed differs from that reported by others in that 20 cc. of freshly voided morning urine is used and the test is done in duplicate; i. e., two mature nonpregnant female rabbits are used for each case. Five cubic centimeters of urine is injected in the morning and afternoon on two successive clays and the ovaries are inspected grossly forty-eight hours after the first injection.
GOLDBERGER MA, SALMON UJ, FRANK RT. VALUE OF FRIEDMAN TEST IN DIAGNOSIS OF INTRA-UTERINE AND EXTRA-UTERINE PREGNANCY. JAMA. 1934;103(16):1210-1212. doi:10.1001/jama.1934.02750420022006