We suggest you examine the following article which addresses clinical cut off points and scoring of the LSNS-6. Scoring for the LSNS-R and the LSNS-18 also can be inferred from this article:

Lubben, J., Blozik, E., Gillmann, G., Iliffe, S., von Rentein Kruse, W., Beck, J.C., & Stuck, A.E. (2006). Performance of an abbreviated version of the Lubben Social Network Scale among three European community-dwelling older adult populations. The Gerontologist, 46(4), 503–513.