Your Rheumie is following technical Rheumatology guidelines.
Any titres of 1:640 or lower with low pretest probability, is of unclear significance, according to the Cleveland Clinic.
In the absence of a positive ENA, I would think that an Anti-dsDNA test would be a useful diagnostic test. If positive it is very indicative of Lupus,but a negative result does not rule it out.
My suggestion would be to have your thyroid FUNCTION checked.
As far as serum testing goes, the most indicative & accurate for cellular thyroid function are: Free T3 (fT3), Free T4 (fT4) AND Reverse T3 (rT3)
All 3 are needed!
fT3/rT3 ratio is probably the most reliable marker for low cellular thyroid function.
To my opinion though we cannot find a better method to test than Dr. Barnes Basal Temperature Test. (there are several versions now)
I have devoted countless of hours, scanning through the studies and groundbreaking work of Dr. Barnes, The Father of Hypothyroidism, lol!
Simply brilliant and way ahead of his time!
Instructions For Taking Basal Body Temperature:
Use an ordinary oral or rectal glass (not digital) thermometer.
Shake down the thermometer the night before, and place it on your nightstand.
The first thing in the morning BEFORE you get out of bed, place the thermometer under your arm for ten(10) minutes.
Record the temperature reading and date right away!
Repeat for 10 days.
Normal Range: 97.6 to 98.2
Averages below indicate hypothyroidism.
Note that in the presence of any infectious conditions, these results may be inaccurate and this could be a problem with chronic low grade infections accompanied by low grade fevers, for the purposes of the temperature testing.
While I'm here, something I should mention that when I had been checking out Dr.Barnes work, one particular finding stayed with me.
From ALL the thousands of patients he treated for hypothyroid
(using natural desiccated thyroid ) NONE of these patients developed Lupus.
The ones who had been already diagnosed with Lupus, NONE developed any new signs of organ involvement, while being treated by Dr. Barnes for hypothyroid.
Also Dr. Lowe from the Fibromyalgia Research Foundation supports the premise that most fibromyalgia patients are either hypothyroid or thyroid hormone resistant.
There are other possibilities, however, the low thyroid function seems to be a very significant and under-looked factor in Autoimmune conditions.
In addition to the thyroid's involvement in cellular waste removal, another process dependent on thyroid function is the activation of enzymes responsible for cellular waste removal.
It is possible the immune system turns against this cellular debris, thus attacking healthy tissue as well in the process.
Also look into Molecular mimicry, an important factor in autoimmune disease.
Let me know if you need any more details.