**2. Urine tests for infectious disease diagnostics and treatment**

A urine specimen is one of the most frequent specimens examined in many of the clinical- and hospital-based laboratories. Urine cultures account for up to 40% of those laboratories' cultures, making it the most common type of culture in such laboratories [27]. Urine is considered an ideal diagnostic specimen for its noninvasive, easy method of collection and the sufficient amount in which it is excreted [14].

The most common infections diagnosed by urinalysis are UTIs, which are one of the most common bacterial infections that require medical intervention. Several other infections such as community-acquired pneumonia and viremia infections can also be diagnosed with the help of urinalysis.

#### **2.1 Urinalysis for diagnosis of urinary tract infection**

UTI affects about 150 million around the globe every year [28]. Urinary tract infections are common in women and to less extent in children. Many women experience multiple infections during their lifetimes. Risk factors specific to women for UTIs include female anatomy. A woman has a shorter urethra than a man does, which shortens the distance that bacteria must travel to reach the bladder [39]. UTIs are generally categorized clinically as complicated and uncomplicated based on the presence of risk factors that comprise the urinary tract or the host defense [40]. Both Gram-negative and Gram-positive bacteria can cause UTIs, with *Escherichia coli* representing about 40–70% of the cases [27].

The diagnosis of UTIs is mainly based on urinalysis and the medical history of the patient, with latter being the most essential element [27].

#### *2.1.1 Sample collection*

Avoiding contamination is a key element when collecting samples for diagnostic purposes. Bacterial contamination of the urine during collection is always a concern, and midstream urine is recommended for UTI. Clear instruction to the patient is indicated to reduce the risk of contamination with the use of clean containers.

**189**

*2.1.5 Pyuria*

*Urine Tests for Diagnosis of Infectious Diseases and Antibiotic-Resistant Pathogens*

tion of the sample is the main disadvantage of this method [43].

Although methods such as suprapubic aspiration and straight catheter technique can reduce or even eliminate the chances of contamination, they are rarely performed as they are not practical for routine cases [27]. Importantly, these methods are invasive, costly, take a lot of time and effort, and are not risk free. Contamination and infection caused by the catheter used to collect the sample is one example [41]. One of the most common method used for the collection of urine is the clean-catch midstream technique [42], which is simple, noninvasive, and risk free and most importantly gives accurate enough results to be used for routine testing. Nonetheless, contamina-

The clinical information obtained from a urine specimen is influenced by the collection method, timing, and handling. An enormous variety of collection and transport containers for urine specimens are available, depending on the type of laboratory test ordered. National Committee for Clinical Laboratory Standards (NCCLS) recommended testing urine sample within 2 hours of collection to avoid false-positive results; however refrigeration or chemical preservation of urine specimens may be utilized if testing or refrigeration within a two-hour window is not possible. A variety of urine preservatives (tartaric and boric acids being the most common) are available that allow urine to be kept at room temperature while still providing results comparable to those of refrigerated urine. Generally, the length of preservation capacity ranges from 24 to 72 hours. Metabolites which can be significantly influenced by the interaction of exposure time and temperature include arginine, glutamine, methionine, phenylalanine, and others, while metabolites which can be significantly

influenced by freeze and thaw cycles are the C3 family and histones H1 [44].

method, and it is not sensitive for detection of low number of bacteria.

insensitive test for concentration of bacteria lower than 105

nitrite, introducing limitation for this test [46].

Bacteria can be simply observed in urine specimens under the microscope, especially after Gram staining. After centrifugation of urine samples, a small amount of the pellet is applied to a glass microscopic slide and stained with the usual Gram-staining protocol. Gram staining can also be done to uncentrifuged specimen; however, there are no definitive criteria to determine positive results with this

Although Gram-staining test can give relatively fast results about the nature of the causative agent; however it is not practical for routine use, it is labor intensive,

*Enterobacteriaceae* are the main causative agent of UTI. They typically produce nitrite, thus making this bacterium chemically detectable. The urine sample for this test should be taken from the first urine produced in the morning, as a minimum of 4 hours are required for the bacteria to produce a detectable amount nitrite. Unfortunately, other bacteria such *as Staphylococcus saprophyticus* cannot produce

The presence of pus in the urine (i.e., pyuria) can be detected by various methods. The best and most accurate method is to microscopically measure the urinary

consuming, making it unsuitable for the patient with uncomplicated UTIs [45]*.*

cfu/mL, and time-

*DOI: http://dx.doi.org/10.5772/intechopen.89231*

*2.1.2 Sample processing*

*2.1.3 Urine microscopy*

*2.1.4 Urine nitrite test*

#### *Urine Tests for Diagnosis of Infectious Diseases and Antibiotic-Resistant Pathogens DOI: http://dx.doi.org/10.5772/intechopen.89231*

Although methods such as suprapubic aspiration and straight catheter technique can reduce or even eliminate the chances of contamination, they are rarely performed as they are not practical for routine cases [27]. Importantly, these methods are invasive, costly, take a lot of time and effort, and are not risk free. Contamination and infection caused by the catheter used to collect the sample is one example [41]. One of the most common method used for the collection of urine is the clean-catch midstream technique [42], which is simple, noninvasive, and risk free and most importantly gives accurate enough results to be used for routine testing. Nonetheless, contamination of the sample is the main disadvantage of this method [43].
