Phytohemagglutinin skin test: diagnostic value for showing immunodeficiency in patients with cancer.

The skin response to 5 mug of purified phytohemagglutinin (PHA) was studied in 299 subjects, including 58 normal controls, 92 patients without malignancies, and 149 patients with nonlymphomatous cancer. Other immunological responses, such as in vitro lymphocyte stimulation (62 subjects) and skin response to purified protein derivatives (PPD) (95 subjects), were tested simultaneously to examine their correlation with the PHA skin test. A positive reaction was observed 24 hr after intradermal injection of 5 mug of purified PHA in 56 (96.6%) of 58 normal controls, 40 (49.4%) of 81 untreated patients with cancer, and 24 (35.3%) of 68 cancer patients receiving anticancer therapy. Among 32 patients with gastric cancer tested, impaired skin reactivity to purified PHA was noted in patients in stage III or IV. A correlation was found between in vivo and in vitro responses to PHA in 46 (74.2%) of 62 individuals (P less than 0.001). The PHA skin test was repeated 4 times over a period of three months in patients without malignancies, and no significant change in tehir skin reactivity was detected. In repeated tests, the skin reactivity to purified PHA of patients with lung cancer varied depending on the clinical status, and the extent and type of anticancer therapy the patients were receiving. It is concluded that the PHA skin test is a simple diagnostic method for screening for immunodeficiency in cancer patients before and during the course of anticancer therapy. Other advantages of this test are that no presensitization is required and that it can be used repeatedly.