What are the diagnostic tests for shingles? I have sharp
shingles without a rash can be diagnosed with PCR (this is the most sensitive and specific test). Since there is no rash, a blood sample has to be used. When the rash develops the doctor should be able to determine the diagnosis without further testing in most cases. PCR testing can also be used when the rash is present and may differentiate herpes zoster (varicella zoster virus) from herpex simplex (herpes simplex virus).
A less sensitive test employs immunohistochemistry to identify abnormal (infected) cells in material from skin scraping. Viral culture is another (less useful) method to diagnose it.
The rash may indeed take a week or so to develop. Your symptoms sound like pain from neural origin. Herpes is obviously a potential cause but other causes are also possible. A bulging intervertebral disc is commonly involved but stenosis (narrowing) of the space between the two vertebrae may be involved as well.
I hope I've answered your question. Please let me know if you need further assistance.