What about the High Dose Hook Effect?

A high dose hook effect is observed, if too much free hemoglobin that is not bound to the gold-labeled antibody reaches the test result region. In this case the antibody immobilized at the test result region becomes saturated with free hemoglobin. This prevents the binding of the hemoglobin complexed with the gold-labeled antibody, thus interfering with the formation of the test result line. The test result appears negative in spite of the presence of hemoglobin in the sample.
The high dose hook effect can be avoided using the color of the sample as a guide. The visual detectable color caused by hemoglobin vanishes between a 10-3 and 10-4 dilution. At this concentration range there is no danger of a high dose hook effect. In contrast samples that are clearly colored due to hemoglobin are likely to cause false negative results because of the high dose hook effect. Good results are obtained when the extract has a "straw" color.
If you are concerned that a negative result is from High Dose Hook Effect, then a simple remedy is to dilute the extract and re-run the sample.