AUDPC

AUDPC stands for Area Under the Disease Progress Curve. It is a quantitative measure used in plant pathology to summarize the overall intensity of a disease in a population over a specified period. The metric integrates disease severity across multiple time points, providing a single value that reflects both the severity and the duration of the epidemic.

Calculation is typically done with disease severity scores collected at known times. If y_i represents the severity at time t_i, the AUDPC is commonly approximated using the trapezoidal rule: AUDPC = sum from i=1 to n-1 of ((y_i + y_{i+1})/2) * (t_{i+1} - t_i). Severity is usually expressed as a percentage (0-100) or a proportion (0-1), and times are days after inoculation or planting. This produces a unit of percent-time or proportion-time, depending on the scoring scale.

Variants and related metrics include relative AUDPC (rAUDPC) or standardized AUDPC, which divide by the maximum possible area to allow comparisons across experiments with different durations or scales. Some studies report AUDPC per unit time (AUDPC/T) or fit smoothed curves to derive alternative summaries of disease progression.

Applications of AUDPC include comparing disease pressure among cultivars, treatments, locations, or years, and assessing the efficacy of control measures. It is particularly useful when disease onset or progression occurs gradually and multiple assessments are available over time.

Limitations of AUDPC include its sensitivity to the timing and frequency of observations and the scoring scale, as well as the assumption of linear change between observation points. Missing data can complicate calculation, and the method may obscure details of the dynamic process such as the rate of spread or the time to first appearance.