people who are asymptomatic have the same precipitins. false negatives are often common with serum precipitins because of lack of testing reagents for many antigens. precipitating igg antibodies against fungal or avian antigens can be detected in the laboratory using the traditional ouchterlony immunodiffusion method wherein 'precipitin' lines form on agar plate. the immunocap technology has replaced this time-consuming, labor-intensive method with their automated cap assays and feia (fluorescence enzyme immunoassay) that can detect igg antibodies against aspergillus fumigatus (farmer's lung or for abpa) or avian antigens (bird fancier's lung). differential diagnosis organic dust toxic syndrome presents similarly with fevers, chills a few hours after exposure to bioaerosols with toxins from fungi, however this is not a true hypersensitivity reaction because it occurs on initial exposure without a preceding sensitization in chronic disease, hp must be differentiated from very similarly presenting idiopathic pulmonary fibrosis. although overlapping in many cases, hypersensitivity pneumonitis may be distinguished from occupational asthma in that it is not restricted to only occupational exposure, and that asthma generally is classified as a type i hypersensitivity. unlike asthma, hypersensitivity pneumonitis targets lung alveoli rather than bronchi. similarly, sarcoidosis has noncaseating granuloma formation, however hilar adenopathy is often seen on chest radiographs. treatment the best treatment is to avoid the provoking allergen, as chronic exposure can cause permanent damage and acute disease is often self-limiting. the identification of the provoking antigen and its location must be ascertained by conducting an exposure assessment. home cleaning is one method of antigen avoidance. if avoidance is not possible, such as in the case of some workplace exposures, minimizing exposure can be accomplished through various means including the implementation of ppe or proper ventilation of a workplace. corticosteroids such as prednisolone may help to control symptoms but may produce side-effects. in the case of severe, end-stage pulmonary fibrosis arising from chronic exposure, lung transplant may be the only viable option. in addition to steroids for fibrotic disease, other immunosuppressants (azathioprine, mycophenolic acid) and anti-fibrotic agents (nintedanib) may be used although their effectiveness is unclear prognosis there are few studies examining longitudinal outcomes in patients diagnosed with hypersensitivity pneumonitis. one study in the us showed about a 0.09 to 0.29 per million increase in mortality rates although the cause specific cause was unclear. most of the outcomes collected are from patients diagnosed with farmer's or bird breeder's lung and thus the degree to which this data can be extrapolated to other types of hp is uncertain. generally outcomes for hp in those with acute disease are very good if exposure is avoided. however, those with subacute or chronic type, especially with biopsy proven fibrosis fair much poorer death rates comparable to people diagnosed with interstitial pulmonary fibrosis. additional images high magnification micrograph of hypersensitivity pneumonitis showing granulomatous inflammation. trichrome stain.