Urine collection pads: are samples reliable for urine biochemistry and microscopy?

Abstract

The aim of the study was to validate the reliability of samples obtained with urine collection pads (UCP) for selected laboratory biochemical analyses, urine cell microscopy, and bedside semi-quantitative stick urinalysis. A series of laboratory experiments was performed to test agreement between urine concentrations, or results, before and after passage through a UCP (incubated for 37 degrees C for 15 min). The following urinalyses were performed: electrolytes, calcium, phosphate, urate, osmolality, pH, protein, catecholamines, toxicology for drugs of abuse, stick urinalysis for glucose, ketones, protein, blood, leucocytes and nitrites, and microscopy for red and white cells. Close agreement was shown for all laboratory analyses except proteinuria, which was underestimated by, on average, 10% after UCP passage. However, stick urinalysis for proteinuria remains sufficiently reliable for clinical use. UCP substantially retain or destroy red and white cells, but stick urinalysis for blood and leucocyte esterase remains reliable. In conclusion, urine samples derived from UCP show good agreement across a clinically relevant range for the biochemical analyses undertaken in this study. Microscopy of UCP samples is unreliable for cellular material but semi-quantitative stick urinalysis for red and white cells is a satisfactory alternative.

Reliability of urine collection pads for routine and metabolic biochemistry in infants and young children

“…This would not be a problem for fresh urine collected directly from an infant as no significant precipitation occurs within the first few hours after collection [5]. All catecholamines showed good agreement between pad and non-pad urine, including samples with very high catecholamine excretion, confirming that use of the pads will give reliable results in children with suspected neuroblastoma or phaeochromocytoma, consistent with previous observations [4]. The pads have not hitherto been evaluated for metabolic tests in children being investigated for inborn errors of metabolism.…”

“…A previous study using the same collection pads demonstrated that routine biochemistry results were similar in pad and non-pad urine obtained from adult volunteers [4]. However, urine obtained from infants and young children has a different composition from adult urine, particularly in relation to lower concentrations of sodium and creatinine.…”

“…These pads resemble a female sanitary pad in size and appearance but are made of plain cotton fibre to facilitate recovery of urine. It has previously been demonstrated that these pads give reliable results for most routine biochemistry tests in adult urine [4]. However, paediatric urine may have a different composition from adult urine, and the pads have not yet been fully validated for use in infants and young children.…”

Urine collected from diapers can be used for 2‐D PAGE in infants and young children

“…While a previous investigation noted comparable total protein values in extracted and spontaneously voided urine, [7] a subsequent study demonstrated a 10% reduction in total protein values in extracted samples. [9] Selective adsorption of specific urine proteins (creatinine, albumin, retinol binding protein) by cotton ball fibers has also been described. [10,11] However, the impact of diaper extraction on the urinary proteomic profile has not been investigated to date.…”

Non-respiratory infections – specific considerations in care homes

“…In men a urethral sheath can be used in patients who cannot produce a specimen whilst, in women, an in-and-out catheter may be the best option 22 . Newcastle urine collection pads (UCPs) represent a non-invasive way of collecting urine, however specimens collected from these are much more useful for dipstick urinalysis than microbiological analysis 35,36 .…”