Abstract: Use of dipsticks to test for the presence of target nucleic acid in a sample solution is described. The dipsticks comprise a contact end for contacting the sample solution and a capture zone, remote from the contact end, to which a capture probe is immobilised. The capture probe is capable of hybridising to the target nucleic acid. The sample solution is contacted with the contact end of the dipstick and travels by capillary action to the capture zone. If target nucleic acid is present in the sample solution it is captured and can be detected at the capture zone. The capture probe is immobilised to the capture zone by a spacer. Use of the spacer increases the stability of the interaction between the capture probe and the target nucleic acid and thus improves the sensitivity of target nucleic acid detection. Detection probes with spacers are also described.