urinekeratansulfaatconcentraties

Urinekeratansulfaatconcentraties (urine keratan sulfate concentrations) refer to the amount of keratan sulfate excreted in urine. They are commonly expressed relative to creatinine (for example micrograms per milligram creatinine) to account for urine concentration, or as total mass per liter.

Keratan sulfate is a sulfated glycosaminoglycan abundant in cartilage and cornea. In healthy people, urinary excretion is low. Elevated urinary keratan sulfate can indicate disorders of keratan sulfate degradation or turnover, most notably Morquio syndrome (MPS type IV) due to GALNS deficiency, and may also be seen in other mucopolysaccharidoses to varying degrees.

Clinical use and interpretation: Urine keratan sulfate testing is used as a screening biomarker for suspected Morquio syndrome and related disorders. A positive or elevated result is followed by confirmatory testing, including enzyme activity assays for GALNS in leukocytes or fibroblasts and genetic testing. Reference ranges vary by assay, age, and laboratory; results should be interpreted in the clinical context and with other diagnostic data.

Measurement methods: Quantification can be performed by colorimetric assays such as dimethylmethylene blue (DMB) or by chromatographic methods including HPLC or LC-MS/MS after enzymatic digestion to keratan sulfate disaccharides. Normalization to creatinine is common to reduce the influence of urine concentration.

Limitations: Urine keratan sulfate is not diagnostic by itself; false positives or negatives can occur due to assay limitations or pre-analytical factors. A definitive diagnosis relies on targeted enzymatic assays and genetic testing, in conjunction with clinical evaluation.