You are correct about the RVUs.
(I'm retyping this so I can make sure I have it right)
You billed:
92928
93458-26-XS-51
The claim came back with:
93458-26-XS
92928
Right?
The edit says "Code 93458 is a column 2 code for 92928 , but a modifier is allowed in order to differentiate between the services provided.
*Use modifier with code 93458.
The current NCCI-associated modifiers are: E1, E2, E3, E4, FA, F1, F2, F3, F4, F5, F6, F7, F8, F9, LC, LD, LM, RC, RI, LT, RT, TA, T1, T2, T3, T4, T5, T6, T7, T8, T9, XE, XP, XS, XU, 24, 25, 27, 57, 58, 59, 78, 79, and 91"
Here's my thoughts; I assume the XS allowed the codes to go through (although it surprises me that they'd allow XS on the same structure/organ).
The multiple procedure rules apply, so if they ranked 93458 first (for whatever reason), then 92928 would get the 50% reduction.
93458-26 has around 9 RVUs
92928 has around 17, but cut in half for multiple procedures, that becomes 8.5, which again, places it second.
I've read in a few places that 93458 with a 26 can cause troubles because the description of that code includes "supervision and interpretation", which is linked to the POS billed apparently...? If that's the case, then they could have dropped the 26 also, leaving 93458-XS with 30 RVUs, give or take. Even if they didn't halve the 92928, the 17 RVUs would still come in second.
If I were to take a guess, I'd say they removed both the 51 and 26 and ended up with 93458-XS, 92928-51, which would explain why they ranked it like they did. I think the multiple procedure rule might be where the payer is getting you caught up. If they allowed the 26 on 93458, the only possible way it could be ranked first is if they cut the 92928 in half. Maybe it's the way the modifiers are ranked? Without personally seeing the RA, that's where I'd end up in my thought process.