Diagnosis of urinary tract infectionA UTI may be suspected based on the symptoms or finding on urinalysis or both, but a urine culture is necessary for confirmation and appropriate therapy. Thus the diagnosis of UTI depends on having the proper sample of urine. There are several ways to obtain a urine sample, some are more accurate than others. These methods are —Midstream urine sample —It is satisfactory in toilet trained children and in circumcised boys. But in young infants and boys who cannot ratract their foreskin, it is not reliable. Such samples will usually reflect periurethral and prepucial organisms and cells.Collection in an adhesive sealed sterile collection bag after disinfection of the genitalsIs a useful technique in infants, but potential contamination from genitals and perianal area can occur.3. Urine specimen through catheterization or indwelling catheter —Urine specimen through a catheter is less likely to be contaminated than the voided specimens as described above. It is also less invasive than suprapubic aspiration, but it is not as sensitive as suprapubic aspiration.A catherized specimen is reliable if the first portion of the urine that may contain urethral organisms is discarded and specimen is taken from later flow through the catheter, but it has the disadvantage of being traumatic and of potentially introducing urethral organisms into sterile bladderSuprapubic aspiration - Suprapubic aspiration is best method to collect urine specimen for culture. It is the most reliable method It can be performed safely in children and in premature infants by 21 or 22 gauge needle. This procedure avoids any sort of contamination, however it is invasive. So it is used only in infants and selected patients. Note:The sensitivity of suprapubic aspiration is 99 %The sensitivity of catherization is 95%