Laboratory parameters of the 1st order – obligatory laboratory tests.
- Urinalysis by test strip:
- A rapid test for nitrite detects nitrite-forming bacteria in the urine, if necessary. [Nitrate detection in urinary tract infection (UTI): 95% with positive nitrate test have positive cultures, however, also 45% with negative test, this especially in infants]
- Likewise, leukocyturia (increased number of white blood cells in the urine) may be detectable. [according to German S3 guidelines, a urinary tract infection (UTI) is considered likely if nitrite or leukocyte esterase test positive].
- Urine pH values > 7.0 in the pH daily profile = indication of a urinary tract infection with urease-forming bacteria (risk of infection stone formation).
- Urine sediment* ; Caution. An isolated hematuria (detection of erythrocytes / red blood cells in the urine) requires a nephrological clarification and follow-up.13% of children with confirmed urinary tract infection by culture showed no pyuria (pus urine): children with E. coli infections showed no pyuria to only 11%, but were enterococci the cause, no pus urine formed in 46%.
- Urine culture* (pathogen detection and resistogram, that is, testing of suitable antibiotics for sensitivity / resistance) from midstream urine or catheter urine – indications:
- Patients with recurrent UTIs.
- Pregnant women
- younger men Note:
- The diagnosis of uncomplicated UTI (cystitis or pyelonephritis) in men is allowed only after exclusion of complicating factors (IIb).
- Men with recurrent UTI should undergo further urologic evaluation (IV-B).
Notice:
- In women who do not have risk factors for complicated UTI (urinary tract infection), typical symptoms (dysuria (pain on urination), pollakiuria (urge to urinate frequently without increased urination), imperative urination (urge to urinate that cannot be suppressed or Can be controlled)) complain, have no vaginal discomfort (itching, altered discharge), in which there is no fever and no flank pain, the presence of uncomplicated cystitis can be assumed with high probability (IIa).A urine culture is not required in women with clear clinical symptoms of uncomplicated, non-recurrent or refractory cystitis.
Systematic screening for asymptomatic bacteriuria (ABU):
- Nonpregnant premenopausal women (life stage: approximately ten to fifteen years before menopause/very last menstrual period): no (Ia-A).
- Pregnancy: no (Ib-B).
- Postmenopause without other relevant concomitant diseases: no (Ia-A).
- Younger men without other relevant concomitant diseases: no (V-A).
- Diabetic patients without other relevant concomitant diseases with stable metabolic situation: no (Ia-B).
- Patients who are about to undergo urological procedures: yes.
Note: Asymptomatic bacteriuria (ABU) is particularly common in the elderly, especially affecting nursing home residents (men 15-40%; women 25-50%).
Criteria for microbiologic diagnosis of urinary tract infection or asymptomatic bacteriuria (ABU)* :
- Urinary tract infection (UTI):
- Pathogen counts > 105 CFU/ml (obtained from “clean” midstream urine).
- Pathogen counts of 103 to 104 CFU/ml may already be clinically relevant in the presence of clinical symptoms (symptomatic patients), provided that they are pure cultures (i.e., only one type of bacteria) of typical uropathogenic bacteria
- Pathogen counts of 102 CFU/ml (at least 10 identical colonies); for urine culture from suprapubic urinary bladder puncture (bladder puncture).
- Asymptomatic bacteriuria (ABU): pathogen counts > 105 CFU/ml of the same pathogen (and same resistance pattern) in two urine samples in the absence of clinical signs of urinary tract infection.
* For the diagnosis of UTI, there must be significant bacteriuria with monoculture and significant leukocyturia. Note: Screening for asymptomatic bacteriuria should not be performed in nonpregnant women without other relevant comorbidities. Urine collection (with the aim of reducing contamination/impurity).
- For an examination of urine sediment or urine culture: obtaining midstream; preparatory measures:
- Infants/toddlers:
- “clean-catch” urine, i.e., the child is held on the lap with genitals exposed and spontaneous micturition (urination) is awaited. The urine is collected with a sterile container.
- Catheter urine or
- Urine by bladder puncture
- Woman:
- Man:
- Careful cleaning of the glans penis (“glans”) of the man with water.
- Infants/toddlers:
- For an orientational urine examination (e.g., by means of test strips), cleaning of the introitus vaginae (vaginal entrance) or glans penis can be omitted.
Thresholds for the diagnosis of different UTI and asymptomatic bacteriuria (ABU).
| Diagnosis | Bacteria detection | Urine collection |
| Acute uncomplicated cystitis in women | 103 CFU/ml | Midstream urine |
| Acute uncomplicated pyelonephritis | 104 CFU/ml | Midstream urine |
| Asymptomatic bacteriuria | 105 CFU/ml |
|
Note: In infants, detection of a urinary tract infection requires: positive findings in urinalysis (leukocyturia and/or bacteriuria) and a count of 105 CFU/ml of a uropathogenic pathogen in a urine sample obtained by catheter or bladder puncture. Second-order laboratory parameters-depending on the results of the history, physical examination, etc.-for differential diagnostic workup
- Small blood count
- Inflammatory parameters – CRP (C-reactive protein) or PCT (procalcitonin).
- Fasting glucose (fasting plasma glucose; fasting blood glucose).
- If necessary, exclusion of a venereal disease (infections that are transmitted primarily through sexual intercourse) – in cystitis with adnexitis (inflammation of the fallopian tube and ovary), colpitis (vaginitis), prostatitis (prostatitis).
- Urine cytology
- BK (polyoma) virus DNA detection – in immunocompromised individuals, BK virus can lead to hemorrhagic cystitis.
