Не могу понять вот этот фрагмент в приведенном ниже предложении:

worsening by increase by

Joint pain/tenderness and joint swelling improvement were defined as decrease by ≥ 30% in score and worsening by increase by ≥ 30% in score.

Чуть больше контекста:

The PsARC method was specifically developed for PsA and used in a large study of sulfasalazin in PsA. It has been assessed in most clinical trials in PsA up to now and it is considered an acceptable primary endpoint. PsARC response was defined as improvement in at least 2 out of 4 measures (patient self assessment, physician assessment, joint ain/tenderness score, joint swelling score) one of which must be joint pain/tenderness score or joint swelling score and no worsening in any of the 4 measures. Improvement or worsening in patient self-assessment and physician assessment were defined as decrease or increase by 1 category on Likert scale. Joint pain/tenderness and joint swelling improvement were defined as decrease by ≥ 30% in score and worsening by increase by ≥ 30% in score. Joint score does not equal joint count. Joint score represents joints scored for severity of pain or swelling on a scale from 0 to 3 and joint count represents number of painful or swollen joints.

Заранее спасибо.