Although plasmatic ADA has been spectrophotometrically determined since 1984, this enzyme is measured especially in fluids, being consecrated as an accurate diagnostic tool of pleural TB or other extrapulmonary TB forms such as meningitis, pericarditis, and peritonitis, with different cut-offs of 40 IU/L or 66 IU/L [33,34]. Here, ADA is linked to infectious meningitis.