I am not on entirely solid ground here, so please correct me if I am wrong about any of this.
I should have been more explicit in my reply. When I was talking to my doctor, it was in regard to specific references in my own medical file, where SICCA and Sjogren's appeared to be used interchangeably. I have Sjogren's along with a collection of other autoimmune and connective tissue diseases, so my umbrella diagnosis is Multiple Autoimmune Syndrome (MAS).
It is my understanding that sicca can refer generically to simply dryness of the eyes and mouth, or it can be used as Sicca Syndrome in which case I believe it is the same as Sjogren's; they both have the same ICD diagnosis code.
Because doctors can use the term referring to just dryness or as another term for Sjogren's, it is very important to understand the context in which it is used. Are they referring only to the symptoms or are they referring to it as a disease?
UCTD stands for "undifferentiated connective tissue disease". I believe Sjogren's is classified as a connective tissue disease, so if someone has Sjogren's they would then have "connective tissue disease" ( technically, the "Undifferentiated" would be dropped).
Since it sounds like Gareth has symptoms of Sjogren's plus Sjogren's antibodies, it would be interesting to find out whether or not they have officially diagnosed him with Sjogren's. And if not, why not? For example, he may have obviously dry eyes but maybe they haven't bothered to prove they are dry with a Schirmer's test.
Never assume that what doctors say and what you hear them say are the same thing. If medical records are not online, where you can verify the diagnosis quite readily, then you may need to request the records and study them carefully. Look closely at the numeric diagnosis codes, which is what they use to bill your insurance.
I was totally shocked when I had finally collected all my medical records, both by what I found and what I didn't find. A surgical biopsy had proven that I had interstitial cystitis over 30 years before I was officially diagnosed with it again; the hospital biopsy report had somehow just been overlooked or misfiled. My doctors reported "suspected connective tissue disease" many decades before it was finally confirmed. I could go on and on, but you get the drift.
What matters most of all is what Gareth's doctor intends "sicca" to mean.