in developing countries , tuberculosis is a major public health issue . because korea is an area endemic for tuberculosis , preventive immunization for tuberculosis is currently performed for infants . even in endemic areas , genitourinary tuberculosis ( gutb ) the number of new patients with tuberculosis in korea was 32,010 ( 67.2 in 100,000 ) in 2002 and 30,687 ( 64 in 100,000 ) in 2003 . in 2008 , the number of new patients with extrapulmonary tuberculosis ( eptb ) was 5,813 , which accounted for 17.0% of all new patients with tuberculosis . repeated acid - fast bacilli ( afb ) stains and cultures of the first urine sample in the morning have been used as conventional and standard tests to confirm urological tuberculosis . because a single sampling of concentrated urine has a sensitivity as low as 30% to 40% , repeated sampling ( 3 to 6 times ) could increase sensitivity up to 80% to 90% and frequently , intravenous pyelogram ( ivp ) , ultrasonography , computed tomography ( ct ) , and magnetic resonance imaging are needed as ancillary studies . in 2000 , the interferon - gamma release assay ( igra ) was developed as a diagnostic tool for tuberculosis . in this method , the amount of interferon - gamma released from t - lymphocytes is measured after the lymphocytes are stimulated with tuberculosis antigen . the quantiferon - tb gold in - tube kit ( cellestis , victoria , australia ) and t-spot.tb ( oxford immunotec ltd . , the clinical sensitivity and specificity of these methods have not been evaluated in urological tuberculosis , however . fifty - seven patients from a single urology clinic with symptoms or radiologic findings suggestive of gutb between march 2009 and august 2011 were evaluated retrospectively . the symptoms suggestive of gutb included dysuria , frequency , urgency or hematuria with sterile pyuria , recurrent or chronic scrotal pain with beaded palpable nodules in the epididymis , and intermittent flank discomfort with radiologically chronic inflammation in the renal pelvis and ureter . the radiological findings suggestive of gutb included renal calcification with chronic inflammatory changes in the kidney , a small contracted bladder and calyceal dilation or destruction with a contracted renal pelvis , and others . patient profiles , clinical presentations , involved organs , and the results of diagnostic tests were reviewed . the evaluation of the patients included detailed medical histories and physical examinations followed by a complete blood count , chemical battery , routine urinalysis , and urine cultures . urine afb stains and mycobacterial cultures sampled in the early morning were obtained either 1 or 2 times . radiologic evaluations included ivp or ct scans of the kidney , ureter , and bladder regions in all patients . this study was approved by the institutional review board of hallym university sacred heart hospital ( institutional review board approval number : 2012-i065 ) . patients who had a history of tuberculosis in other organs , including the lung and lymph nodes , were excluded from this study . the patients were tested by use of the urine afb stain , urine afb culture , urine tuberculosis polymerase chain reaction ( ut - pcr ) , and igra . the commercially available quantiferon - tb gold in - tube kit ( cellestis ) was used for the igra . for the quantiferon - tb gold in - tube assay , 1 ml of whole blood was added to each of the three qft - tb tubes : the tb antigen tube ( esat-6 , cep-10 , and tb 7.7 ) , the mitogen - positive control tube ( phytohemagglutinin ) , and the negative control tube . the tubes were treated according to the recommendations of the manufacturer ( cellestis ) , and the interferon ( ifn)-gamma concentrations ( iu / ml ) of the plasma were measured by use of an enzyme - linked immunosorbent assay reader . an ifn - gamma concentration 0.35 iu / ml ( tb antigen minus negative control ) was considered a positive test result . when the mitogen - positive control concentration was not higher than 0.5 iu / ml , an " indeterminate test result " was reported . the results of urine afb and culture , radiological studies , ut - pcr , and igra were compared descriptively . among the 57 patients , 36 ( 63.1% ) were male and the others ( 36.9% ) were female . for the chief complaint , 22 patients had flank pain , 11 had dysuria , 11 had gross hematuria , 5 had fever , and 5 had scrotal pain . three patients complained of nonspecific symptoms such as general myalgia , fatigue , or weight loss . the organs involved that were suspicious for tuberculosis clinically or radiologically were the upper urinary tract in 38 patients , the bladder in 5 patients , and other genital organs in 14 patients . radiologically , 30 patients ( 52.6% ) had findings suspicious of urologic tuberculosis , and 19 of these patients showed a positive result on the igra ( table 2 ) . the result of the urine afb stain was positive only in 5 patients ( 8.8% ) , and urine culture was positive in 7 patients ( 12.2% ) . all the patients who showed positive results in the urine afb stain also had a positive urine culture ( table 2 ) . all patients who showed positive results on the urine afb stain and culture also had positive results on the igra ( table 3 ) . nine patients had a positive result for tuberculosis in the urine ut - pcr . among these ut - pcr - positive patients , the afb stain and culture were positive in 6 patients ( 66.6% ) ; however , a ut - pcr - negative patient was reported as having a positive result for the afb stain and culture for tuberculosis ( table 3 ) . gutb was first described by willbolz et al . ( quoted from ) , and it represents tuberculosis that has spread to the kidney , ureter , testis , and epididymis via a blood - borne infection . recently , as a subtype of eptb , it was reported to account for < 1.5% of patients with pulmonary tuberculosis . in korean reports , 0.4% of all patients with tuberculosis were found to have gutb . compared with pulmonary tuberculosis therefore , the incidence of eptb , as well as of gutb , might be underestimated . unfortunately , the treatment is usually delayed because of delayed symptom presentation and delayed definitive diagnosis . consequently , a number of patients present with nonfunctioning kidneys , ureteral strictures , and contracted bladders . because the clinical symptoms of gutb are nonspecific and the diagnostic procedure for gutb is somewhat complicated for patients , clinicians may miss the diagnosis of gutb , and proper treatment may be delayed in order to undergo surgery . accordingly , simpler and more efficacious diagnostic tools are necessary for early diagnosis . the nonspecific symptoms of gutb make it difficult to define inclusion criteria for patients for the evaluation of new diagnostic tools . investigators should always consider the diagnosis of gutb in a patient presenting with vague , long - standing urinary symptoms ( dysuria , hesitancy , and frequency ) for which there is no obvious cause . the symptoms and signs of gutb vary in both intensity and duration . in the published literature , the most common presenting symptoms in patients with gutb are irritative voiding symptoms , flank pain , and hematuria , which are reported around 60% and 50% of the time . the patients in the current study also complained of similar nonspecific symptoms : flank pain was reported in 22 patients ( 38.5% ) , dysuria was reported in 11 patients ( 19.3% ) , and hematuria was reported in 11 patients ( 19.3% ) . radiologic abnormalities suggesting gutb are found in 63% to 95% of patients in the literature , and in the present study , such evidence was found in 52.6% of the patients . the urine afb stain and culture are the reference standards for the diagnosis of tuberculosis . a definite diagnosis of gutb is confirmed by isolation of mycobacterium tuberculosis ( mtb ) in the urine afb stain and culture . however , these tests have their own limitations for use in clinical circumstances , because the discharge of organisms into the urine is sporadic , and few organisms are involved . direct smears often show negative findings and often can not differentiate tuberculous from nontuberculous mycobacteria . although culture is a more sensitive diagnostic tool , it takes 6 to 8 weeks to get the results because of the slow growth rate of mycobacteria . in the current series , although it can not yet replace afb stain and culture , because tuberculosis pcr is more specific , more sensitive , simpler , and faster than an afb stain of a direct smear , it is currently used as a useful supplementary tool . however , the efficacy of pcr for the diagnosis of eptb , including gutb , is not conclusive . a pcr test of a specimen excised from the organs suspicious for eptb would be very helpful for the diagnosis ; however , because of the low sensitivity of ut - pcr , gutb can not be excluded from the differential diagnosis . when pulmonary tuberculosis is suspected on the basis of clinical symptoms but the results of afb stain and culture are negative , the igra for tuberculosis can be helpful . it is especially useful as a diagnostic tool in developed countries , in which the tuberculosis incidence is less than 1% . although , in such endemic areas where bcg vaccination is a nationwide prevention policy , a meta - analysis of the pooled sensitivity of igra for tuberculosis was 70% to 78% and the specificity was 99% among patients who did not receive bcg vaccination and 96% among bcg - vaccinated persons . another merit of the igra is that only one test is required to obtain high sensitivity . in a previous korean study , song et al .   reported that the sensitivity and specificity of the igra for eptb were 69% and 82% , respectively . among the enrolled patients , there were only two gutb cases . in the current study , 30 patients had a positive result on the igra for tuberculosis ; however , only 7 patients had positive results on the afb stain and culture tests . if we assume that the afb stain and culture tests are standard diagnostic methods , the 23 igra - positive patients might be considered to be false - positives . otherwise , when we propose that the specificity of the igra is around 95% on the basis of the pulmonary tuberculosis study , these patients would get the benefit of timely treatment . the low sensitivity values of the afb stain and culture tests are a very strong limitation . a potential bias of this study may result from the fact that it was a retrospective review . for the proper diagnosis of gutb , 3 to 6 urine samplings are required to reach a sensitivity of around 90% . in this retrospective review , however , only 1 or 2 urine samplings were obtained . therefore , on the basis of the results of this study , it is not reasonable to determine that igra is superior to afb stain and culture for the diagnosis of gutb . on the other hand , when the results from other tests are not reliable in a clinical situation , the igra can be helpful for diagnosis . interestingly , a ut - pcr - negative patient was diagnosed with gutb by afb stain and culture and igra results . even though this is just one case , clinicians can consider using the igra as a supplementary test for the diagnosis of gutb , either in combination with ut - pcr or alone . in conclusion , the igra is a simple test , and it is feasible as a supplementary and screening diagnostic tool for gutb . because the current retrospective study has several biases and limitations , the authors are planning to perform a prospective study by using the same sampling protocols with clear inclusion criteria . the igra for tuberculosis is a fast and simple serum test that might feasibly be used as a supplementary or screening tool for the diagnosis of gutb in addition to urine afb stain and culture . further studies for statistical evaluation of its sensitivity , specificity , and efficacy are needed .
purposeto evaluate the feasibility of the interferon - gamma release assay ( igra ) as a supplementary diagnostic tool for the diagnosis of genitourinary tuberculosis ( gutb).materials and methodsfifty - seven patients who were tested with the igra to diagnose gutb were included . 
 all patients had clinical or radiologic features suspicious for gutb . signs and symptoms included chronic dysuria with long - standing sterile pyuria , renal calcification with distorted renal calyces and contracted renal pelvis , and chronic epididymitis . 
 patients who had a history of tuberculosis in other organs were excluded . 
 tests including igra , urine acid - fast bacilli ( afb ) stain and culture , urine tuberculosis polymerase chain reaction ( ut - pcr ) , and radiological examinations were performed to confirm gutb . 
 the medical records of the patients were reviewed retrospectively.resultsthe igra result was positive in 30 patients ( 52.6% ) . 
 the results of the urine afb stain and culture were positive in 5 patients ( 8.8% ) and 7 patients ( 12.2% ) , respectively . 
 the results of ut - pcr were positive in 9 patients ( 15.8% ) . 
 the 7 patients who showed positive results in the urine afb stain and culture also had positive results on the igra . a ut - pcr - negative patient was diagnosed with gutb by positive results on both the igra and afb stain and culture.conclusionsthe igra might feasibly be used as a supplementary or screening tool for the diagnosis of gutb in addition to urine afb stain and culture . 
 further studies for statistical evaluation of its sensitivity , specificity , and efficacy are needed .