[users@httpd] apache config check for non available field in request

[alchemist vk]

Hi All,
 Consider the request curl -vk -X POST -H "Del-Auth: abcd" '
127.0.0.1/test/newuser' where I intentionally wont provide content type
header for new user creation.

While trying to write apache config file to check the presence of
content-type field in request header, I am not able to do it..

Please help me in checking presence of header via config file.

Tried as *RewriteCond %{HTTP:Content-Type}  ' ' *, but it didnt work..

Thanks in advance
A