Prior to 3GPP rel 8 sNonIntraSearch could only be RSRP based.
In 3GPP rel 9, the standards split the above threshold into 2.
One is sNonIntraSearchP that is RSRP based and the second one is sNonIntraSearchQ which is RSRQ based.
So basically the UE can now make reselection decisions based on quality as well as signal strenght/pathloss.
You can still use the “old” sNonIntraSearch with rel9 and later UEs (backwards compatible).
So, P refers to RSRP and Q refers to RSRQ.
If RSRQ parameters are configured then both RSRP & RSRQ based measurement need to be satisfied.