This verse is a parenthetical statement given by Luke by way of explanation (see 1.18-19). On Trophimus, see 20.4 and 2 Timothy 4.20.

In some languages it is not possible to combine a series of terms merely with prepositional links—for example, Trophimus from Ephesus with Paul in the city. Rather, one must say “they had seen Trophimus going around with Paul in the city; Trophimus was from the city of Ephesus.”

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on The Acts of the Apostles. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .