If the KMO<=0.6 (better is 0.7 but practically 0.6 is a good value) you can drop the variables with the lowest individual KMO statistic values, until KMO overall rises above .60. That is, in SPSS check KMO and Bartlett's test of sphericity and also check Anti-image. In the SPSS output examine the diagonal elements on the Anti-image correlation matrix are the KMO individual statistics for each variable. You will drop the variablew with smallest KMO one by one.
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