Leucine Aminopeptidase (LAP) Assay Kit – Bulk Reagents


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Selling unit: per 100ml

Product Name

Common name: Leucine aminopeptidase (LAP) assay kit (L-leucyl-p-nitroaniline substrate method)

English name: Leucine aminopeptidase (LAP) Assay Kit (L-leucyl-nitroaniline substrate method)

Reagent Ratio

Single, 3:1, 4:1, common ratio single reagent, other ratios need to be customized

Intended Use

Used to determine the viability of LAP in human serum.

LAP is widely distributed throughout the human body, with the highest levels in the liver, gallbladder, kidney, small intestine and myometrium. A significant increase in blood LAP is seen in hepatocellular carcinoma, biliary tract cancer, pancreatic cancer, obstructive jaundice, and acute hepatitis; a moderate increase is seen in chronic hepatitis, cirrhosis, pregnant women, and habitual drinkers.2. An increase in urinary LAP is seen in acute nephritis, renal tubular injury, renal failure, renal tumors, and female genital tumors. The change of urinary LAP can timely respond to the degree of renal tubular injury and recovery, which is meaningful for the early diagnosis and efficacy observation of kidney disease.3. The use of sulfonamides, aminoglycoside antibiotics, such as gentamicin and tobramycin, polymyxin, contrast agents and PSP injection can increase LAP.

Test Principle

The activity of leucine aminotransferase in the sample can be calculated by measuring the rate of change of absorbance of p-nitroaniline at 404 nm by the rate method using L-leucyl-p-nitroaniline as the substrate.

Main Components

Reagent components included in the product.

Leucine Aminopeptidase (LAP) Assay Kit

*Components are not interchangeable in kits with different lot numbers.

*Reagent components not included in the product, but necessary for the test: outsourced normal and abnormal QCs and calibrators.

Storage Conditions And Expiration Date

The kit is stored at 2-8°C away from light and is valid for one year.

Reagents that have been opened are taken care not to be contaminated and the reagents are stabilized in the instrument compartment (2-8°C) for one month.

The reagents must not be frozen.

Applicable Instruments

Hitachi 7180/7600; Olympus AU680/2700; Toshiba TBA120; Myriad BS2000M/480; Siemens ADVIA1800/2400 automatic biochemical analyzer.

Sample Request

Serum. Blood should be collected intravenously and separated promptly after collection to avoid hemolysis.

The LAP in the samples was stable for 7 days at 2-8°C.

Test Method

  1. Reagent preparation: liquid reagents are ready to use out of the bottle.
  2. Test conditions: (The following parameters are set in accordance with Toshiba TBA120FR, and different on-board parameters can be requested according to different testing instruments)

Leucine Aminopeptidase (LAP) Assay Kit

Single reagent operation procedure.

Leucine Aminopeptidase (LAP) Assay Kit

Dual reagent operation procedure.

Leucine Aminopeptidase (LAP) Assay Kit

*Reagents and sample volumes can be increased or decreased in proportion to the requirements of different biochemical analyzers.

  1. Calibration procedure.

Randox Laboratories Ltd UK is recommended to use the calibration serum produced by Randox Laboratories Ltd. The Randox calibration serum is selected by NAGEL 37°C.

  1. QC control procedures.

It is recommended to use quality control sera produced by Randox Laboratories Ltd UK, Landau Laboratory Diagnostics Ltd. It is recommended that each laboratory establish its own QC system and select appropriate QCs for quality control. The QC values should be within the specified range. If outside the specified range, it is necessary to take appropriate measures or contact the manufacturer.

  1. Calculation.

Sample concentration = (sample ΔA /min) / (standard ΔA /min) × standard concentration

Reference Interval

Serum: 12-37 U/L

The blood samples of 150 normal people were selected by clinical trials, measured by automatic biochemical analyzer, and the values obtained were processed statistically and reference ranges were calculated. It is recommended that each laboratory establish its own reference range of normal values.

Interpretation Of Test Results

The determination of LAP in serum is only one of the indicators used by the clinician to make a diagnosis of the patient. The clinician must also make a comprehensive judgment based on the patient’s physical symptoms, medical history, and other diagnostic items and diagnostic tools.

Limitations of the test method.

There was essentially no effect on the measured values for bilirubin ≤ 40 mg/dL, hemoglobin ≤ 500 mg/dL, ascorbic acid ≤ 30 mg/dL, and celiac disease ≤ 500 mg/dL.

Product Performance Index

Appearance: The appearance of the kit should be neat and clean, with clear identification of text symbols and intact reagent bottles; R1 is a colorless or light yellow clarified liquid, R2 is a colorless clarified liquid, both without precipitation, suspension and flocculent.

Absorbance of reagent blank: wavelength 404 nm, optical diameter 1.0 cm, temperature 37°C, A0  ≤ 0.5.

Absorbance change rate of reagent blank: ΔA/min ≤ 0.001 at wavelength 404 nm and optical diameter 1.0 cm.

Analytical sensitivity: The kit tests 15 U/L of the test substance with absorbance change rate ΔA/min ≥ 0.003.

Linearity interval: test serum samples, in the range of 14 to 300 U/L, the linear correlation coefficient |r| should not be less than 0.990, the absolute deviation of linearity in the interval of 14 to 35 U/L should not exceed 3.5 U/L, and the relative deviation of linearity in the interval of (35 to 300 U/L should not exceed ±10%.

Precision: repeatability CV ≤ 5%; relative extreme difference between batches ≤ 10%.

Accuracy: Relative deviation ≤ 10%.


  1. This product is for in vitro diagnosis only.
  2. Avoid contamination when using the reagent, the container used must be clean, and please take necessary precautions, do not swallow, and avoid contact with skin and mucous membrane.
  3. Do not mix R1 and R2 into a single reagent.
  4. When changing the reagent lot number, please recalibrate.
  5. There may be differences in the use of reagents from different manufacturers for the same sample.
  6. All sample cassette reaction waste should be treated as an infectious source and the operator needs to take the necessary protective measures.
  7. test tubes and other instruments that have come into contact with the test sample should be disposed of in accordance with medical waste disposal methods.
  8. The calibrator and quality control are made from human matrix sera, which have been tested for HIV (HIV1, HIV2) antibodies, hepatitis B surface antigen (HbsAg) and hepatitis C virus (HCV) antibodies and found to be negative, although the assay is highly accurate and cannot guarantee that all infected donors can be detected, so the quality control should also be treated as an infectious specimen.


  1. Hu W P, Hu Y Y et al. Significance of serum leucine aminopeptidase in the diagnosis of hepatobiliary diseases and tumors. Practical Liver

Journal of Disease, 2004,7 (1):35 -36.

  1. Goldbarg JA, Rutenberg AM. The colorimetric determination of leucine

aminopeptidase in urine and serum of normal subjects and patients with cancer

Cancer 1958, 11: 283 -291

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