The Cytobacteriological examination of urine (CBEU), a cornerstone of medical bacteriology laboratories, stands as the gold standard test for confirming urinary tract infections (UTIs) [1] . Notably, according to the Burkina Faso AMR surveillance annual reports, UTI accounted for approximately half of the analysis requests [2] . Nevertheless, resource-limited countries grapple with the substantial cost and availability barriers associated with CBEU utilization. Such constraints compel clinicians facing clinical suspicion of UTIs to initiate presumptive antibiotic treatments that often lack precision, thereby fostering the escalation of antibiotic resistance [3] [4] .

In this context, the urinary dipstick test (UDT) emerges as a potential alternative [5] . A meta-analysis conducted in 2004 found that UDT has moderate sensitivity (48%) and better specificity (91%) in detecting UTIs. Sensitivity is higher in inpatients (58% vs. 45%), while specificity is greater in outpatients (96% vs. 85%) [6] . Semi-quantitative urine dipsticks encompass key markers such as leukocyte esterase, nitrite (an indicator for enterobacteria), and secondary proteins that indicate UTI. Implementation of this test offers the prospect of initiating or withholding treatment while awaiting CBEU results, where applicable [7] [8] [9] . In our resource-constrained setting, scant investigations have delved into the assessment of UDT’s contribution to UTI diagnosis, particularly among inpatients. Given the dynamic nature of infectious epidemiology, our study endeavors to assess the role of urine dipsticks in detecting UTIs among patients admitted to Sourô Sanou University Hospital.

The aim of our study was to assess the potential of UDT in screening for UTIs among hospitalized patients within the resource-constrained context of low-income countries.

UDT parameters that best predict UTI: Leukocyte esterase and the nitrite test are two markers traditionally examined for UTI screening [12] . Notably, the nitrite test displayed relatively low sensitivity (33%), while the leukocyte esterase test exhibited modest specificity (59%), findings aligned with those of various studies [12] [13] [14] [15] . Our multivariate analysis further corroborates these observations, revealing that the combined assessment of nitrites, leukocytes, and protein yields superior predictive power for UTI, surpassing the performance of leukocytes and nitrites alone (p = 0.008). Incorporating hematuria, however, did not yield additional insight into UTI occurrence (p = 0.06). In the existing literature, several authors have advocated for combining nitrite and esterase screenings as a screening approach [12] [16] . In the broader population, transient proteinuria has been linked to UTI [17] [18] . Our bivariate analysis concurs, exhibiting a statistically significant association between proteinuria and UTI (p = 0.002). Hematuria’s significance varies in upper urinary tract infections, particularly in diagnosing cystitis. Its presence is often indicative of UTIs associated with lithogenic bacteria, such as Proteus mirabilis, Klebsiella spp., or Corynebacterium urealyticum, which are less prominent in our study cohort [19] [20] .

Intrinsic performances of UDT: Sensitivity ranged between 3% and 82%, while specificity varied from 57% to 98%, contingent upon the specific parameters assessed. Notably, the most robust performance was observed with the combination of nitrite and leukocyte assessments. Particularly, the greatest sensitivity (82%) was achieved when UTI was defined as the presence of either leukocytes or nitrites on the UDT. The simultaneous presence of leukocytes, nitrites, and proteins resulted in enhanced specificity (98%). The analytical performance of urine strips in our study mirrors that of the study of Kayalp et al. in 2013 in a microbiology laboratory in Ankara, Turkey [21] . This study reported a sensitivity and specificity of up to 78.8% and 97.8%, respectively.

Nonetheless, other analytical parameters such as likelihood ratios demonstrated weaker outcomes compared to findings from several other investigations [12] [16] [22] . The diagnostic gains, assessed through likelihood ratios (LR+ and LR−), ranged from 1.9 to 2.8 and 0.3 to 0.8, respectively. Likelihood ratios, derived from the interplay of sensitivity and specificity, offer insight into the likelihood of accurately confirming or ruling out UTIs based on UDT results. Our study’s diagnostic gain, although relatively modest, is consistent with the established analytical performance of UTI screening, which generally remains moderate across diverse populations. Comparatively, findings from a systematic review by John et al. in the United States indicated more robust diagnostic gains, with LR+ ranging from 4.27 to 29.3 and LR- from 0.22 to 0.54 [16] .

Variations in UDT performance in UTI screening according to epidemiological factors: The performance of UDT displayed marginal disparities based on sex, age, urinary catheterization, and ongoing antibiotic therapy. Minor elevations in sensitivity (83% vs. 81%) and NPV (88% vs. 84%) were noted in women as opposed to men. Inherent characteristics like sensitivity and specificity, distinct from urine dipsticks, remain relatively unswayed by disease prevalence [23] . Predictive values, representing post-test probabilities, accommodate these variables, particularly the prevalence of UTI [24] . This discrepancy could underpin the superior NPV exhibited in women. The findings of Yusuf et al. in a parallel study also documented a higher NPV in women than in men (94.7% vs. 83.3%) [9] . These findings align with established literature where multiple studies endorse UDT application in women due to its enhanced capability to exclude UTI [9] [12] [16] . Contrastingly, in men, UDT’s relatively lower NPV restricts its capacity to confidently exclude UTI, thereby rendering its PPV more valuable in practice. The elevated PPV in men (60% vs. 58%), as noted by other researchers, can be attributed to the heightened occurrence of upper UTIs, particularly prostatitis, characterized by elevated bacteriuria [20] . UDT’s efficacy was more pronounced among younger patients than their elderly counterparts. Diagnosed efficiency was indeed greater (0.75) among the young demographic, accompanied by a slightly higher NPV (85% vs. 84%). Yusuf et al. also highlighted UDT’s better performance in younger patients, especially in terms of NPV compared to adults (97.1% vs. 94.9%) [9] . Correspondingly, UDT’s aptitude for excluding UTI, notably among the youth and even in asymptomatic children, where a negative UDT can confidently eliminate UTI, reinforces its clinical utility [20] [25] . Our study revealed a higher diagnostic efficiency in non-catheterized patients (E = 0.70 vs. 0.59) and individuals not hospitalized in high-risk units (Nephrology and Urology) (E = 0.73 vs. 0.63). Notably, UDT’s proficiency is more adept at detecting community acquired UTIs than nosocomial ones. The primary advantage of urine strip screening in hospitalized patients lies not in its performance, as it’s less sensitive than culture, especially in cases of low bacteriuria and antibiotic usage, common in this patient category. Instead, it’s the convenience of bedside application that holds value [24] . In patients with urinary catheters, the prevalence of UTI is notably high, escalating with the duration of catheterization to stabilize around the 30^th day. Moreover, UTIs in this population often involve microorganisms that lack nitrate reductase production, such as staphylococci, enterococci, Candida spp., or Acinetobacter spp. [19] . Consequently, UDT is specifically indicated in these cases for asymptomatic infection screening, particularly in preoperative evaluations for invasive procedures within the genitourinary sphere. In these contexts, UDT, driven by specificity and NPV, cannot substitute CBEU, which necessitates an immediate execution [9] [24] [26] .

Limitations of the urine dipstick Test: The limitations observed in the Urine Dipstick Test (UDT) performance can be attributed to several factors.

· Detection Threshold and Sensitivity: UDTs highlight leukocytes through the detection of leukocyte esterase from both intact and lysed leukocytes. However, their detection threshold is around 10 leukocytes per mm³, which is relatively higher compared to the sensitivity of microscopy cytology, capable of detecting less than 10 leukocytes/mm³ [19] [27] . The UDT model used in our study only identifies nitrites when bacteriuria exceeds 10⁵ elements/mm³, a threshold considerably higher than CBEU’s ability to detect bacteriuria from 10³ elements/mm³. This disparity results in false negatives for bacteriuria levels ranging between 10³ and 10⁵ elements/mm³, which corresponds to the pathogenicity threshold for group 1 and 2 uropathogens, including enterobacteria, commonly isolated in our study [17] [19] [27] .

· Nitrate Reductase Production and Specificity: The exclusive production of nitrate reductases by enterobacteria contributes to the test’s poor sensitivity and low negative predictive value (NPV). Nitrites are present in urine only when bacteria with nitrate reductase activity, particularly enterobacteria, convert dietary nitrates into nitrites [13] [20] . This limitation renders UDT capable of detecting only enterobacteria and not Gram-positive bacteria such as staphylococci and non-fermentative Gram-negative bacilli, constituting about 25% of the isolated strains in our study [17] . While this characteristic contributes to the high specificity of up to 98%, it restricts the scope of the test.

· Interference from Chemical Substances: Interference from various chemical substances can influence UDT parameters, particularly in a specific population. Antibiotic usage, which was reported in 42% of patients in our study, could potentially decrease the sensitivity of UDT in detecting leukocyte esterase. Metabolites of drugs with oxidative potential, including cephalosporins, tetracyclines, nitrofurantoin, doxycycline, and gentamicin, may lead to false negatives when testing for leukocyte esterase [17] [19] [20] .

· Optical Reading and Standardization: Optical (naked eye) reading of test strips, as employed in our study, may introduce variations and limitations in accuracy. The accuracy of UDT heavily depends on strictly adhering to reading times. Automatic reading methods utilizing spectrophotometers have been reported to offer superior results. By enabling standardized readings, these techniques enhance analytical characteristics like repeatability and reproducibility, indirectly influencing the analytical performance of the tests [19] [22] [28] .

This study sheds light on the predictive potential of the combined nitrite, leukocyte, and protein test results in urinary tract infection (UTI) screening using the UDT. UDT demonstrated higher specificity than sensitivity, with consistent performance across various epidemiological characteristics of UTI. Particularly, UDT was found to be more effective in excluding UTI in specific groups, such as women, young patients, or those without urinary catheters. Our findings underscore the importance of using UDT judiciously due to its propensity for false negatives, which can impact its reliability as a UTI diagnostic tool. Furthermore, we affirm that UDT, even when positive, serves primarily as a reference test aimed at reducing unnecessary treatments, and should not be regarded as a definitive method for diagnosing UTI. A study encompassing a larger population, particularly focusing on outpatients, and incorporating spectrophotometric strip reading, holds promise for evaluating UDT’s potential in excluding CBEU. Such research would contribute to optimizing diagnostic resources in our resource-constrained setting and guide informed clinical decision-making.

Abdoul-Salam Ouédraogo: Initiation, design, and scientific guarantor of the study; André Nagalo: file review, data entry, data analysis, bibliographic research, and writing of the article; Odilon D. Kaboré, Senkaye-Lagom Aimée Kissou and Boukary Kabré: first reading and reorientation of the manuscript; the other authors reviewed the manuscript and made corrections. All authors read and approved the final version of the manuscript.

The authors would like to thank all the technical staff of the bacteriology laboratory at the Sourô Sanou University Hospital for their contribution to the analysis of the study samples.

The authors declare no conflict of interest.

Nagalo, A., Kaboré, O.D., Kissou, S.-L.A.,. Kafando, H., Kabré, B., Zongo, E., Ouattara, C.A., Sawadogo, Y., Semdé, A., Zoungrana, J., Poda, A., Godreuil, S. and Ouédraogo, A.-S. (2023) Can the Urine Dipstick Test Be an Alternative in the Screening of Urinary Tract Infections for Inpatients in the Context of a Low-Income Country? Advances in Infectious Diseases, 13, 627-640. https://doi.org/10.4236/aid.2023.134051