FIGURE 1.

Criteria evolution during eight rounds of Delphi. The X-axis represents each R and the Y-axis the cumulative number of data entries. R1 started with 338 criteria (arrow) which were narrowed down to 66 in R5 and remained 66 in R6. The criteria were further narrowed down to 35 (comprising eight differential diagnosis) in R7. R6 and R7 were two validation rounds and R9 was the control round also called the definition round. Abbreviations: Clin-, clinical data negative; Clin+, clinical data positive; #D, differential diagnosis; EM-, electron microscopy negative; EM+, electron microscopy positive; IF-, immunofluorescence microscopy negative; IF+, immunofluorescence microscopy positive; Lab-, laboratory negative; Lab+, laboratory positive; LM-, light microscopy negative; LM+, light microscopy positive.