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Radioactivity measurements involve counting the characteristic atomic disintegrations of an isotope followed by complex statistical calculations. Each measurement has its own minimum detectable concentration, or MDC, which varies depending upon sample amount and elapsed time of the measurement. Therefore, each sample result consists of three different values - the calculated activity, the total propagated uncertainty (TPU), and the MDC, reported as: Activity, +/- TPU, MDC. For example, Radium-228 = 6.2 +/- 1.8, 0.95 pCi/L.

Because of the extreme sensitivity of nuclear measurements, test results are sometimes reported in scientific notation.