Rationale and objectives: Both subcutaneous and intradermal injections are used for the scintigraphic investigations of the superficial lymphatic system. The qualitative differences between these types of injections are well known. This study quantified their differences in a group of volunteers.
Methods: With the limbs at rest, activities in the axillary nodes (AxN) were recorded at 1, 20, 40, 60, 80 and 100 min after subcutaneous or intradermal injection of TC-labelled human serum albumin nanocolloids in the ventral middle part of each forearm of nine young, healthy, male volunteers and the results were compared.
Results: Expressed as per 10,000 of injected activity, activities recorded in the AxN were significantly higher (32.5 times as a mean value, ranging from 8.4 to 130.7 times) after intradermal injections than after subcutaneous injections (P<0.001 by using two-tailed Wilcoxon's signed-rank test). The mean AxN activity after intradermal injections was also apparently higher for the right limbs than for the left limbs, but when the paired t-test was used to compare the right with the left values of the nine volunteers, the comparison did not reach statistical significance (at T+100, 2P=0.087). When their handedness is taken into account, however, a level of statistical significance is reached (at T+100, 2P=0.025).
Conclusion: This study quantifies the differences between subcutaneous and intradermal injections, but also shows, although on a limited number of volunteers, that handedness influences the results of the intradermal injections.