When you do nwa.com OLCI for an international trip it will ask you to type in your passport number during OLCI (so have it handy). After that, most likely nobody from NW will look at your passport unless you check bags. You may need to show it to KL or AMS security personnel when entering the AMS gate area for your flight to CAI, however, and obviously you'll need to show it to Egyptian immigration on arrival in CAI.

Note that on the way back you can only do OLCI through klm.com (not nwa.com). klm.com OLCI does not qualify for Xtreme Miles points, and you also may not be able to print your BP (only certain origins allow home-printed BPs), but at least you'll get a better choice of seats for CAI-AMS