.It is a very good question and asking good question indicate good thinking. The topic is full of uncertainties. When does a common cold become an acute sinusitis? How often does it follow a cold? How often there is a spontaneous recovery? How easy will it be for a researcher to have an access to such a patient? At what point viral a sinusitis becomes a bacterial sinusitis? If I were to do a basic research I would to base the research at primary care level and try to access all patients who present with a cold. These patients are naturally not very popular with the physician because they are considered to be time waster but would provide an unique opportunity for comprehensive research for acute sinusitis. Pain and pyrexia has to be the basic criteria of acute sinusitis. Middle meatal swab ( pre antibiotics) might clarify the bacterial situation. Obviously this is not an answer but a further invitation for answers.

In my opinion the EPOS guide of the European Academy of Alergology and Clinical Inmunology is the best and updates the contents regularly. 

European position paper on rhinosinusitis and nasal polyps. European Academy of Alergology and Clinical Immunology.

The EPOS document is available as a free download at www.rhinologyjournal.com, and defines acute post viral sinusitis. Supporting evidence from bacterial cultures, which can be taken as an endoscopically guided middle metal swab (there is good evidence to show equivalence with the 'gold standard of sinus puncture) are useful for directly antibiotic choice, but not essential for diagnosis

I appreciate your answers. Thank you, dear colleagues.

I asked the question to see if anybody shares my opinion on the current situation. Both EPOS and IDSA have their own guidelines, which are very thorough and vast reports on rhinosinusitis. Though, both guidelines rely a lot if not mostly on symptom-based diagnosis. Many studies has shown, that both viral and bacterial acute rhinosinusitis have very similar symptoms and thus are very difficult to differentiate.

There are only few studies where diagnosis of microbiologically confirmed acute maxillary rhinosinusitis is studied thoroughly. I think this issue is also considered in the guidelines mentioned before. Currently, I think that both EPOS and IDSA criteria for diagnosing bacterial rhinosinusitis are not tight enough. Many of my patients meet the guideline criteria for prescribing antibiotics even though the patients clearly don't need them and are cured with symptomatic medication and time. So, my opinion is that there is still much to do in developing guideline for diagnosing acute bacterial rhinosinusitis. I am more than happy to continue this conversation if anybody wishes to share their opinion or disagree with me.

I am very happy that this Q&A in ENT field started, and thanks of the people who founded this.

in my idea  still needs more study and making new guideline for diagnosing and treatment of acute rhinosinusitis.

As we all know, mucopurulent discharge in middle meatus, or even opaque sinus are not indicators of bacterial sinusitis; I would think of antibiotics when symptoms (as pain) and signs (as fever) with the adove-mentioned criteria are met with and persists more than 2 days, and affecting normal activities and productivity;

I think this area needs more and more researching efforts, and i must thank Dr Timo Autio for his good way of thinking in a daily-pracised problem. 

Diagnosis of acute bacterial sinusitis is mainly clinical and may be associated with facial pain mucopurulent nasal discharge lasting for more than 3 days elevated temperature and general feeling of being unwell.

Quite often viral rhino sinusitis can develop into bacterial infection due to secondary infection.

Middle meatal swab cultures and plain sinus xrays may e considered if there is lack of response to usual conservative measures but generally not necessary.

I recently read the guidelines for treatment of acute bacterial sinusitis in Choosing wisely I found this a useful and sensible approach.

You may like to check this.

EPOS guide...

indicators of 2ry bacterial following acute primary viral sinusitis:

mucoid discharge change to mucopurulent

rise of temperature

increasing nasal stiffness , congestion and headche

diagnosis is confirmed by culture of nasal discharge obtained endoscopically from the middle  meatus.