Anatomy of a Lab Test Inquiry

Jacques Benveniste’s work involved a technique that is used in Europe--but not in the United States--to determine if an individual is allergic to specific chemicals such as ragweed dust and pollen. White blood cells called basophils from the person to be tested are combined in a test tube with the chemical thought to be causing the reaction.

If the tested person is allergic to the chemical, the basophils will interact with it and be changed so that they can no longer be stained by a certain dye. The results are readily determined by counting the number of cells in a specific volume of blood whose color changes when the dye is added.

Benveniste used a special antibody that reacts with basophils like an allergen. He reported that the antibody solution continued to prevent staining of the basophils even when it had been diluted so much that, theoretically, no molecules of the antibody should be present.

The Nature investigative team observed seven series of dilutions. In all cases, the number of stained cells were counted by Dr. Elisabeth Davenas, whom Benveniste described as having the greatest success in getting the assay to “work.” In three cases, the stained cells were also counted by a second technician.

In the first three tests, Davenas knew the identity of the samples she was counting, and the results matched those previously reported by Benveniste. In the fourth case, the identity of the samples was partially hidden, and the results also matched the previous reports.

In the last three experiments, however, the observers completely masked the identity of the samples and the numbers of stained cells were counted by both Davenas and the technician. In all three cases, contrary to the earlier report, diluted antibody solutions had no effects on the basophils.

The observers concluded that unwitting bias on the part of Davenas was a major explanation for the previously reported results.