Confirm testing two days prior to sailing……If we sail on a Saturday, test on either Thursday or Friday? Thanks!

[CHEZMARYLOU]

We changed our flight for October cruise so we only have one night in Florida. I HATE to have to fly in one day early in March coming from the North East.

[Bjbilly]

I wish they would go back to the 3 day test it would make things so much easier

[Fouremco]

3 hours ago, D C said:

Higher 'accuracy' with lower risk of a false positive.  

 

Good info on the rapid tests here:

https://www.fda.gov/medical-devices/letters-health-care-providers/potential-false-positive-results-antigen-tests-rapid-detection-sars-cov-2-letter-clinical-laboratory

 

These 3 bullet items really scream "remember that these rapid tests really aren't that good"

 

• Consider the CDC's recommendations when using antigen testing in nursing homes and other settings. For positive results, especially in low incidence counties, consider performing confirmatory RT-PCR test within 48 hours.
• Remember that positive predictive value (PPV) varies with disease prevalence when interpreting results from diagnostic tests. PPV is the percent of positive test results that are true positives. As disease prevalence decreases, the percent of test results that are false positives increase.
  • For example, a test with 98% specificity would have a PPV of just over 80% in a population with 10% prevalence, meaning 20 out of 100 positive results would be false positives.
  • The same test would only have a PPV of approximately 30% in a population with 1% prevalence, meaning 70 out of 100 positive results would be false positives.  This means that, in a population with 1% prevalence, only 30% of individuals with positive test results actually have the disease.
  • At 0.1% prevalence, the PPV would only be 4%, meaning that 96 out of 100 positive results would be false positives.
  • Health care providers should take the local prevalence into consideration when interpreting diagnostic test results.
• Consider positive results in combination with clinical observations, patient history, and epidemiological information.

Thank you. I suspected that might be the case but wasn't sure. Interestingly, but perhaps not surprisingly, the CDC has a somewhat different take:

 

The specificity of antigen tests is generally as high as most NAATs, which means that false positive test results are unlikely when an antigen test is used according to the manufacturer’s instructions.  

https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html

 

I guess we all have our own comfort zone. I fully respect your decision and the reason for it, but I'm comfortable with taking the antigen test. Hopefully neither of us will have a false positive reading.

[D C]

3 hours ago, Fouremco said:

Thank you. I suspected that might be the case but wasn't sure. Interestingly, but perhaps not surprisingly, the CDC has a somewhat different take:

 

The specificity of antigen tests is generally as high as most NAATs, which means that false positive test results are unlikely when an antigen test is used according to the manufacturer’s instructions.  

https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html

 

I guess we all have our own comfort zone. I fully respect your decision and the reason for it, but I'm comfortable with taking the antigen test. Hopefully neither of us will have a false positive reading.

Ironically, I'm favouring a PCR despite being on the wrong side of a PCR false positive a year or so ago. I want every last bit of 'accuracy' I can get. 

 

(3 PCR tests in 4 days. positive, negative, negative)

[Ipeeinthepools]

18 hours ago, D C said:

Higher 'accuracy' with lower risk of a false positive.  

 

Good info on the rapid tests here:

https://www.fda.gov/medical-devices/letters-health-care-providers/potential-false-positive-results-antigen-tests-rapid-detection-sars-cov-2-letter-clinical-laboratory

 

These 3 bullet items really scream "remember that these rapid tests really aren't that good"

 

• Consider the CDC's recommendations when using antigen testing in nursing homes and other settings. For positive results, especially in low incidence counties, consider performing confirmatory RT-PCR test within 48 hours.
• Remember that positive predictive value (PPV) varies with disease prevalence when interpreting results from diagnostic tests. PPV is the percent of positive test results that are true positives. As disease prevalence decreases, the percent of test results that are false positives increase.
  • For example, a test with 98% specificity would have a PPV of just over 80% in a population with 10% prevalence, meaning 20 out of 100 positive results would be false positives.
  • The same test would only have a PPV of approximately 30% in a population with 1% prevalence, meaning 70 out of 100 positive results would be false positives.  This means that, in a population with 1% prevalence, only 30% of individuals with positive test results actually have the disease.
  • At 0.1% prevalence, the PPV would only be 4%, meaning that 96 out of 100 positive results would be false positives.
  • Health care providers should take the local prevalence into consideration when interpreting diagnostic test results.
• Consider positive results in combination with clinical observations, patient history, and epidemiological information.

 

I'm not sure you are presenting an accurate impression oy the accuracy of antigen tests and the chance of false positives.  From the CDC web site:  

 

https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html

 

"The specificity of antigen tests is generally as high as most NAATs, which means that false positive test results are unlikely when an antigen test is used according to the manufacturer’s instructions."

 

Much of the discussion in the article you reference discuss the impact of the test not being performed correctly and how do you determine the amount of Covid infection in a community.  The testing for cruisers is only trying to determine if a specific person has Covid not how many people in the community have Covid.  

 

All tests will have some false positive results but antigen tests do not have a significantly higher rate of false positive tests. 

[awhfy]

On 9/17/2021 at 9:04 AM, Missymo said:

• For sailings that require a pre-cruise test, you will be asked to take the test no more than 3 days before your sail date for UNVACCINATED (UNDER 12)guests and no more than 2 days for VACCINATED  How to calculate 3 and 2 days before: The day you set sail is not included as one of the days. For example,UNVACCINATED if you are setting sail on a Saturday, you can take your test on Wednesday, Thursday, or Friday before your sailing and for VACCINATED  2 days you can take the test Thursday or Friday.
• Make sure that your selected test provider can provide you a valid results document in time for your travel.      
• For fully vaccinated guests living in the United States, a home-test kit is available for purchase on our Website. We are working with Optum, an authorized medical provider to offer this option to our guests. Complete your pre-cruise test kit at home or any place of your choosing with the help of live video supervision by a Certified Guide. 

 

TEST KIT - SHIPPING TIMES

We recommend ordering your test kit at least one full week before you plan to take your test. If you’re in a pinch, see below to understand if your order will arrive in time.

 

ORDER TEST KIT ON:                                GET TEST KIT NO LATER THAN:

Monday                                                        Thursday evening

Tuesday                                                        Friday evening       

Wednesday                                                  Monday evening

Thursday                                                       Tuesday evening   

Friday                                                            Wednesday evening

Saturday                                                       Wednesday evening

Sunday                                                          Wednesday evening         

 

 

This has been changed to 2 days

[D C]

21 minutes ago, Ipeeinthepools said:

 

I'm not sure you are presenting an accurate impression oy the accuracy of antigen tests and the chance of false positives.  From the CDC web site:  

 

https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html

 

"The specificity of antigen tests is generally as high as most NAATs, which means that false positive test results are unlikely when an antigen test is used according to the manufacturer’s instructions."

 

Much of the discussion in the article you reference discuss the impact of the test not being performed correctly and how do you determine the amount of Covid infection in a community.  The testing for cruisers is only trying to determine if a specific person has Covid not how many people in the community have Covid.  

 

All tests will have some false positive results but antigen tests do not have a significantly higher rate of false positive tests. 

The positive predictive value (PPV) is dependent on the expected percent positive within the population.  The lower the expected percent positive, the greater the chance of a given positive test being false.  The FDA article is warning about the likelihood of a positive test being incorrect based on the expected infection rate in the population. 

 

1000 people getting on a ship.  If we expect 1% are actually positive, that's 10 people.   We expect 990 false tests.  But at a specificity of 98%, only 970 of those people test negative, and 20 receive a false positive. 

 

If the sensitivity is also 98%, all of the positive people actually test positive. 

 

So 30 people test positive and 20 of those are false positives. 

 

As the CDC says, false positives are unlikely.  970 out of 990 is pretty good...unless you're on the wrong side of those odds.  Remember, the CDC is currently in the business of pushing testing. The FDA is not. The CDC uses far softer language like "unlikely".  A specificity of 51% makes it unlikely. 

 

The advertised sensitivity and specificity are also based on lab tests where everything is perfect. Every last bit of specificity matters. 

 

 

 

[Ipeeinthepools]

5 minutes ago, D C said:

The positive predictive value (PPV) is dependent on the expected percent positive within the population.  The lower the expected percent positive, the greater the chance of a given positive test being false.  The FDA article is warning about the likelihood of a positive test being incorrect based on the expected infection rate in the population. 

 

1000 people getting on a ship.  If we expect 1% are actually positive, that's 10 people.   We expect 990 false tests.  But at a specificity of 98%, only 970 of those people test negative, and 20 receive a false positive. 

 

If the sensitivity is also 98%, all of the positive people actually test positive. 

 

So 30 people test positive and 20 of those are false positives. 

 

As the CDC says, false positives are unlikely.  970 out of 990 is pretty good...unless you're on the wrong side of those odds.  Remember, the CDC is currently in the business of pushing testing. The FDA is not. The CDC uses far softer language like "unlikely".  A specificity of 51% makes it unlikely. 

 

The advertised sensitivity and specificity are also based on lab tests where everything is perfect. Every last bit of specificity matters. 

 

 

 

 

You're exactly right and it really doesn't matter to the person getting an antigen test to board the ship.

I expect that there will be a couple of positive cases on every sailing, there's no way to keep it off the ship.  The fact that everyone above 12 is vaccinated and everyone has some type of pre-boarding test make the ship a very safe environment.  Vaccination and sensible precautions will protect most cruisers.  If your number is correct at 2% false positives, how many of those 2% are because the test was done incorrectly?  Again the fact that an antigen test has a specificity of 98% and another test has a specificity of 99% is not significant to the average cruiser.

 

 

[Honeybadger418]

Hi all,  this discussion about pre-travel Covid testing makes me wonder about my June 2022 cruise out of Rome.  

 

Our plan is to spend 4 days in Rome pre-cruise.  If Covid tests are required 72 hours before boarding the ship, that means we would have to get tested in Rome?

 

 

[Fouremco]

11 minutes ago, Honeybadger418 said:

Hi all,  this discussion about pre-travel Covid testing makes me wonder about my June 2022 cruise out of Rome.  

 

Our plan is to spend 4 days in Rome pre-cruise.  If Covid tests are required 72 hours before boarding the ship, that means we would have to get tested in Rome?

 

 

Covid tests must be taken within 2 days of embarkation, so yes, you would need to be tested in Rome.

[TeeRick]

3 hours ago, Honeybadger418 said:

Hi all,  this discussion about pre-travel Covid testing makes me wonder about my June 2022 cruise out of Rome.  

 

Our plan is to spend 4 days in Rome pre-cruise.  If Covid tests are required 72 hours before boarding the ship, that means we would have to get tested in Rome?

 

 

Yes but by June who knows? And Celebrity might be subject to the requirements for Italy and wherever your ship stops.

[LGW59]

3 hours ago, Honeybadger418 said:

Hi all,  this discussion about pre-travel Covid testing makes me wonder about my June 2022 cruise out of Rome.  

 

Our plan is to spend 4 days in Rome pre-cruise.  If Covid tests are required 72 hours before boarding the ship, that means we would have to get tested in Rome?

 

 

I’d not worry about this as it is 9 months out.  Lots can and will change between now and then.

[mayleeman]

A false positive will result in not cruising but you are entitled to a refund (or optional FCC) under the extended CWC protocol.

 

A false negative, however, could result in infecting several other cruisers aboard, who might have more a severe Covid experience, or who might spread it to more people.  

 

The percent of false negatives seems more important from a public health standpoint. The "window" of infectiousness may be shorter for vaxxed, so the risk from those false negatives is lower, but there is no risk at all to other people from a false positive.

 

Anyone know the relative accuracy rates of the two tests with regard to false negatives?

[D C]

4 minutes ago, mayleeman said:

A false positive will result in not cruising but you are entitled to a refund (or optional FCC) under the extended CWC protocol.

 

A false negative, however, could result in infecting several other cruisers aboard, who might have more a severe Covid experience, or who might spread it to more people.  

 

The percent of false negatives seems more important from a public health standpoint. The "window" of infectiousness may be shorter for vaxxed, so the risk from those false negatives is lower, but there is no risk at all to other people from a false positive.

 

Anyone know the relative accuracy rates of the two tests with regard to false negatives?

I'll have to look up the sensitivity of each type (which varies from brand to brand, of course), but pcr are better at not giving false negatives. 

[TeeRick]

On 9/25/2021 at 4:13 PM, mayleeman said:

A false positive will result in not cruising but you are entitled to a refund (or optional FCC) under the extended CWC protocol.

 

A false negative, however, could result in infecting several other cruisers aboard, who might have more a severe Covid experience, or who might spread it to more people.  

 

The percent of false negatives seems more important from a public health standpoint. The "window" of infectiousness may be shorter for vaxxed, so the risk from those false negatives is lower, but there is no risk at all to other people from a false positive.

 

Anyone know the relative accuracy rates of the two tests with regard to false negatives?

A false negative is not ideal but it will happen on occasion.  But probably (hopefully) not much of an impact on a fully vaccinated ship.  

[Ipeeinthepools]

48 minutes ago, TeeRick said:

A false negative is not ideal but it will happen on occasion.  But probably (hopefully) not much of an impact on a fully vaccinated ship.  

 

I'll suggest that a larger risk might be getting infected after you take the test and then boarding the ship.  I'm sure that Celebrity is collecting the data on how many vaccinated people are testing positive and are prevented from boarding and how many vaccinated people are testing positive during the cruise.  If the numbers are low enough, perhaps it isn't worth the effort for the vaccinated people to get tested.

[TeeRick]

27 minutes ago, Ipeeinthepools said:

 

I'll suggest that a larger risk might be getting infected after you take the test and then boarding the ship.  I'm sure that Celebrity is collecting the data on how many vaccinated people are testing positive and are prevented from boarding and how many vaccinated people are testing positive during the cruise.  If the numbers are low enough, perhaps it isn't worth the effort for the vaccinated people to get tested.

Yes hopefully we will get back to that.  But it seems that the data from actual cruises does not seem to matter.  CDC makes proclamations and cruise lines follow.

[D C]

1 hour ago, Ipeeinthepools said:

 

I'll suggest that a larger risk might be getting infected after you take the test and then boarding the ship.  I'm sure that Celebrity is collecting the data on how many vaccinated people are testing positive and are prevented from boarding and how many vaccinated people are testing positive during the cruise.  If the numbers are low enough, perhaps it isn't worth the effort for the vaccinated people to get tested.

Or being infected and pre-symptomatic at the time the test was taken.  Sensitivity (false negatives) is not good in that situation.   At least one NIH paper questions the use of rapid tests to find covid in asymptomatic people because the sensitivity is below the WHO recommendation of 80% sensitivity.  (PMC 8178956)

Edited September 27, 2021 by D C

[Ipeeinthepools]

2 hours ago, TeeRick said:

Yes hopefully we will get back to that.  But it seems that the data from actual cruises does not seem to matter.  CDC makes proclamations and cruise lines follow.

 

I think the CDC recommendations expire at the end of October, I wonder if they will extend them.

[DCPIV]

On 9/24/2021 at 2:34 PM, lovecruzin said:

It would be nice if the rules for vaccinated were 3 days for PCR and 2 days for Antigen. I guess that would create even more confusion! I would prefer to do PCR but timing doesn't work.

 

That's what it was.  Just judging by the chatter around CC, it caused quite a bit of confusion.