Or in other words,
NF
n = NF
1 + (NF
2 – 1)/Gain
1 + (NF
3 – 1)/(Gain
1 – Gain
2) + ….. + (NF
n – 1)/(Gain
1 – Gain2 ….. Gain
n-1)
where item 1 is the RF amp, 2 is the mixer, and so on.
I-f filter loss, unless grossly high, won't have an affect on MDS in receivers that have a reasonable amount of gain ahead of the filters - an rf amplifier and mixer for example. 15 - 20 dB of 'front end' gain will make 10 dB loss that follows invisible as far as noise figure or MDS is concerned.
An unusual receiver like the Squires SS-1R, with only a single relatively low gain active stage (on 40 meters), would be more likely to suffer MDS degradation with high filter loss.