Performance of the Urine Leukocyte Esterase and Nitrite Dipstick Test for the Diagnosis of Acute Prostatitis

To the Author—We read with great interest the report by Koeijers et al. [1] evaluating the urine dipstick test in afebrile male outpatients with urinary tract infection (UTI), and were surprised that the results were the opposite of those usually observed in female patients with uncomplicated cystitis. We used the same approach in a nested study that included 136 inpatients with community-acquired acute prostatitis and systemic symptoms (fever in 86% of patients, painful prostate noted by digital rectal examination in 68%, a positive blood culture results in 20%) from a retrospective, multicenter study [2]. The bacterial titers in the 136 urine analyses were as follows: ⩾105 cfu/mL for 56 patients (41%), 104 cfu/mL for 15 patients (11%), 103 cfu/mL for 8 patients (6%), and ⩽102 cfu/mL for 57 patients (42%). Of these 57 patients, 24 had received antibiotic treatment before analysis, and 50 had leukocyte counts of >104 cells/mm3. Eighty-one percent of the isolated bacteria were nitrite-producing Enterobacteriaceae. The performance findings for the dipstick urinary test are presented table 1, as organized according to the bacteria load cutoff considered for the diagnosis of UTI in male subjects (either 103 or 104 cfu/mL). The best positive predictive values (94%–98%) were attained when both nitrites and leukocytes were detected, and the highest negative predictive values (65%–73%) were attained when either leukocytes or nitrites alone were detected. Performance of the urine dipstick detection of nitrites and leukocytes for the diagnosis of acute prostatitis. Two cutoff diagnostic bacteria loads (103 and 104 cfu/mL) were tested, because this value remains controversial in the literature [5, 6]. We noticed minor variations in the performances of the dipstick urine test between the 2 cutoff values, likely because our patients had high bacteria loads. We found that the dipstick urinary test had a high positive predictive value and a low negative predictive value for the diagnosis of acute febrile prostatitis, as Koeijers et al. [1] found for nonfebrile male patients with UTI. These performances were exactly the opposite of those usually observed for uncomplicated acute cystitis in women (i.e., high negative and low positive predictive values), for which recommendations usually agree that the test should be used to exclude infection [3, 4]. We agree with the conclusions of Koeijers and colleagues that, for symptomatic male patients, a positive nitrite test result should be considered indicative of a UTI and that a negative nitrite test result should not exclude the diagnosis of UTI, so that a midstream urine sample should be cultured. It is clear from the data from the study by Koeijers et al. [1] and from the data presented here that, for these patients, the sensitivity (55%–58%) and negative predictive value (42%–49%) are too low for the nitrite test result alone to be used to exclude the diagnosis of UTI in male subjects. Thus, unlike the diagnosis of uncomplicated acute cystitis in women, the dipstick test for the rapid detection of leukocytes and nitrites should be used to diagnose acute prostatitis and UTI in nonfebrile male subjects and not to exclude them. However, Koeijers et al. [1] concluded that treatment should not be started when the nitrite test result is negative, pending the results of the urine culture. We think that this conclusion has to be balanced. Indeed, most of the male patients with UTI, like those described in our series, are febrile and require urgent antibiotic treatment because of a high risk of urosepsis and because of a poor tolerance of symptoms [3, 7]. In these cases, we would recommend starting antibiotic treatment after collection of the midstream urine sample, even when the dipstick test result comes back negative for nitrites. The urine dipstick test should be routinely performed for the management of UTI in male subjects, with awareness of its high positive and low negative predictive values. Potential conflicts of interest. All authors: no conflicts.