This can mean a number of things. However, in most cases this anomaly is caused by what we call "secondary flow" and commonly occurs when the sample pad is not cut off at test completion. If the pad is not cut off, liquid in the sample pad will continue to flow up the strip as it is drying which may cause a light false positive to appear. In this case, we recommend retesting the sample and cutting off the sample pad after you have interpreted your result according to test instructions.
Results interpreted after the assay time has expired are not as reliable as when completed per the test instructions.
Agdia puts a great deal of effort into developing all of our ImmunoStrip tests. We strive to ensure that our ImmunoStrip tests are as sensitive and accurate as their ELISA counterparts, where available. In fact, many customers are not aware that they can achieve the same level of reliability and confidence, while saving time and money, using ImmunoStrip tests compared to ELISA methods.
During the development process we look at as many analyte and host variations as possible to ensure the highest level of accuracy. If we are aware of any non-specific reactions to a sample matrix or other analyte, it will be posted in the test user guide.
All of our ImmunoStrip tests are guaranteed to meet QA specifications for one year from the date of purchase.
Providing the test container was sealed and desiccated, the tests should still work fine. All of our ImmunoStrip tests undergo rigorous stability studies to ensure they can withstand periods of time outside of our recommended storage conditions, such as shipment.
However, if your container was left open there is a chance they have absorbed moisture and may no longer work according to our quality assurance standards. Please be sure to always keep the strip container closed when not in use.
Most often, "green lines" are caused because the sample extract is too concentrated. To fix this problem, you can try further diluting your existing extract with buffer, or prepare a new extract using less plant tissue.
If you are unable to retest the extract in one of the ways described above, the result can be interpreted as negative providing it has no red or purple hue. However, we strongly encourage a retest when this occurs because the green line can potentially mask low level positive results.
Agdia products have been developed to be highly sensitive and specific while also being robust enough to withstand temperature fluctuations and unrefrigerated storage during shipping. The storage and incubation temperatures listed on our products and user guides reflect the average conditions observed in our laboratories. To ensure that your test is performing optimally, we recommend storing the refrigerated components at 2 - 8 °C (36 to 46 °F). When performing the test or storing components at room temperature, we recommend a range of 21 +/- 3 °C (65 to 75 °F). In many situations, temperature fluctuations beyond those listed above may not significantly affect the outcome of a qualitative test , however, Agdia can only guarantee test performance within the recommended temperature ranges. We understand that temperatures at your location may be different from those in our test validation laboratory, so if you have concerns about your local conditions, please feel free to contact us at 1-800-622-4342, or firstname.lastname@example.org or email@example.com.
Is your control line darker than the test line and clearly visible? If not the test may be invalid. Several factors can cause an invalid test, including improper storage and submerging the ImmunoStrip too far in the sample extract.
If the control line is valid, then you may be seeing a light positive that is caused by a low titer sample. If the pathogen or analyte titer is too low, or approaching the tests LOD (Limit of Detection), weak results are expected.
One remedial approach would be to retest a fresh sample taken from symptomatic leaves. Although many of our ImmunoStrip tests can reliably detect asymptomatic samples, the sample may be newly infected and the pathogen concentration may be too low for detection.
This means the test result is invalid. An invalid test result is most generally caused by oversubmersion of the test strip in the sample. When running an ImmunoStrip test, make sure the test strip is only submerged about 1/4" into the sample. The furthest a test strip should be inserted into a sample is to the white line on the green label located below the sample arrows. Other causes, although very rare, could be the test is not compatible with the sample type you are testing, the test was not stored properly, or the test is past its expiration date. For more information please contact Agdia.