WHO typically follow the DSM, however; not always. WHO do do things slightly different, though they normally allow the APA to do the ground work, review it, then make their changes based on, most likely, less input and more reliance on the DSM. You have to think about global standardisation as to both parties reasons. The DSM also mimic some aspects of the ICD from WHO.
Both books contain comprehensive data. People get all wrapped up in diagnostic criterion, which is not accurate. Diagnostic criterion is purely one part of the process. If you look into an ICD or DSM, you will find each diagnosis has like its own little chapter, of sorts. There is a lot of relevant information surrounding each diagnosis which must be used.
WHO publish diagnostic criterion online, and Behavenet publish the DSM diagnostic criterion online, in conjunction with approval from the APA. Both books are copyright, and the diagnostic criterions published are only a very small part of the actual books themselves. The books are copyright, hence the information pertaining to each diagnosis is not published, thus you must buy the book to read it and know it.
This is why people self-diagnosing have a very limited view of the complete picture. Also why many physicians / people diagnosing, get it wrong, as most don't even review the literature and instead use a position of estimation, guessing and worse, empathy and such, to apply diagnoses to people. This is often why a counsellor, psychologist and psychiatrist will all have different views on what diagnosis should be given, let alone peers within a group often under test environments all coming to different views and diagnostic outcomes, when it comes to mental health.
Right now, the ICD has a bare blank "Complex Post-Traumatic Stress Disorder" heading there, awaiting to see what the DSM did. The ICD next release isn't until 2014 / 2015 from memory... so it will take time to see if they use the sub-type of the DSM and create an actual CPTSD diagnosis, or whether they follow under PTSD with a sub-type to cover complex trauma. Time will tell... again, the WHO sometimes do things differently, though they usually both stick together for the majority of diagnoses overall, only changing symptoms or severities or such, i.e. slight changes though maintaining global diagnostic consistency.
