Suppose we are interested in pairs of siblings, one of with cancer (case) and one without (control). We wish to see if cancer treatment increases the risk of acquiring a psychiatric disorder when corrected for a covariate, iq. Such an analysis is possible in SPSS using the Cox regression procedure as outlined under the section entitled conditional logit models (about two-thirds of the way down the page) at http://www2.chass.ncsu.edu/garson/pa765/logit.htm The straightforward generalisation to three or more dichotomous matched responses is also described.

Below is an illustrative example of the described procedure on the sibling cancer data.

Running the Cox Model below

COXREG
  case_con  /STATUS=duplic(1)  /STRATA=pair
  /CONTRAST (disorder)=Indicator
  /METHOD=ENTER iq  /METHOD=ENTER disorder
  /PRINT=CI(95)
  /CRITERIA=PIN(.05) POUT(.10) ITERATE(20) .

The disorder term in the regression gives the odds 1/0.553 = 1.81 with 95% confidence interval of (1/3.192, 1/0.096) = (0.31,10.42). The cancer treatment increases the odds of having a psychiatric disorder by 1.8 however this is not statistically significant. (chi-square(1)=0.45, p=0.50).