Figure 2. Correlations between interferon-γ responses to PHA and various mycobacterial antigens.
N = number of infants who responded to both antigens considered. Rho: Spearman's rank correlation coefficient; IFN-γ: interferon-gamma; PHA: phytohaemagglutinin; PPD: purified protein derivative; Ag85: antigen 85; STCF: short term culture filtrate; KMTB: killed Mycobacterium tuberculosis.