Error parsing ORU_2.4

[rf1234]

I'm getting this error when trying to get ObservationValue:
"Cannot assign a TdiST_24 to a TdiST_24"

It is a "strange" error...

MSH|^~\&|APPOLO|LABSUITE|APPOLO|LDPSFT|20151102091739||ORU^R01|1863520|P|2.4
PID|||330742^^^LDSPFT^MR||RESULTADOS^TESTE^ENVIO||19450923000000|F|||Posto CDFT
ORC|SC|38795064|11193981_591|3681960|CM||||20151027125230|EL0028
OBR||38795064|11193981_591|591^Hepatite D - VHD, Ac. Delta IgM||20151027125230|20151028165359|20151031111111
OBX|1|ST|591.000000002_16870_TX^Hepatite D - VHD, Ac. Delta IgM||N\XE3\o reactivo|11/02/2015 09:16||0||N|F|||20151029140223|EL0028