DLD Histamine Elisa

Storage and Stability 
The kit is shipped at ambient temperature. Upon arrival, store the kit at 2 – 8 °C to keep it stable until its expiry date. Once opened the kit is stable until its expiry date. The shelf life of the ready-to-use reagents is indicated on the respective bottle label. For stability of prepared reagents refer to 6.1. Reagents must equilibrate to room temperature before use and refrigerated immediately after use.

Plasma
EDTA- or heparin plasma can be used. However, as Histamine concentrations have been found to be lower in EDTA-plasma, it is recommended to use heparin plasma. Haemolytic, lipaemic and icteric samples should not be used. The samples can be stored up to 6 hours at 2 – 8 °C. For a longer storage (up to 6 months) the samples must be frozen at -20 °C. 
Urine Spontaneous urine can be used for this test as well as collected urine. In the case of collected urine, the total volume of urine excreted during a 24-hours period should be collected and mixed in a single bottle containing 10 – 15 ml of 6 M hydrochloric acid as preservative. Avoid exposure to direct sun light. Determine the total volume and take an aliquot for the measurement. For patients with suspected kidney disorders the creatinine concentration should be determined in addition. Urine samples can be stored at -20 °C for at least 6 months.

Calculation of the Results 
On a semi logarithmic graph paper the concentration of the standards (x-axis, logarithmic) are plotted against their corresponding optical density (y-axis, linear). When using analysing software, it is recommended to use the Four Parameter Logistic (4PL) Regression (alternatively: cubic-spline or logit-log). Alternatively, the optical density of each standard and sample can be related to the optical density of the zero standard, expressed as the ratio OD/ODmax, and then plotted on the y-axis. When using analysing software, it is recommended to use the Four Parameter Logistic (4PL) Regression (alternatively: cubic-spline). The concentration of the controls and EDTA-plasma, heparin plasma and cell culture media samples in ng/ml can be read directly from the standard curve. The read concentration of urine samples in ng/ml must be multiplied by a factor of 5. 
The read concentration of the heparin whole blood samples in ng/ml must be multiplied by a factor of 26. 
The read concentration of the stool samples must be multiplied by a factor of 150, which accounts for the amount stool used in the assay. The result is expressed as ng/g. 
Conversion: Histamine: 1 ng/ml corresponds to 9.0 nmol/l