user52815: I've been using Blocktrail's API:
https://www.blocktrail.com/api/docs/lang/nodejs#data_overview
to get data for the following unspent address on the testnet: 
2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j.
Blocktrail's API returns the index as 4, whereas blockexplorer's:
https://testnet.blockexplorer.com/api/addr/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/utxo
and smartbit's APIs:
https://testnet-api.smartbit.com.au/v1/blockchain/address/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/unspent
both return an index of 0. Am I missing something here?

user2306: 
both return an index of 0. 

0 is the correct answer here.

Am I missing something here?

Not sure.
I can't reproduce your problem. I'm querying blocktrail like this:
curl https://api.blocktrail.com/v1/tbtc/address/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/transactions?api_key=MY_APIKEY

and that returns all of the transactions for the address, none of which have an index of 4.
Can you post the line of code that calls their API?

52815: <p>I've been using <a href="https://www.blocktrail.com/api/docs/lang/nodejs#data_overview" rel="nofollow noreferrer">Blocktrail's API</a>:</p>

<p><a href="https://www.blocktrail.com/api/docs/lang/nodejs#data_overview" rel="nofollow noreferrer">https://www.blocktrail.com/api/docs/lang/nodejs#data_overview</a></p>

<p>to get data for the following unspent address on the testnet: </p>

<p>2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j.</p>

<p>Blocktrail's API returns the index as 4, whereas blockexplorer's:</p>

<p><a href="https://testnet.blockexplorer.com/api/addr/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/utxo" rel="nofollow noreferrer">https://testnet.blockexplorer.com/api/addr/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/utxo</a></p>

<p>and smartbit's APIs:</p>

<p><a href="https://testnet-api.smartbit.com.au/v1/blockchain/address/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/unspent" rel="nofollow noreferrer">https://testnet-api.smartbit.com.au/v1/blockchain/address/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/unspent</a></p>

<p>both return an index of 0. Am I missing something here?</p>
 2306: <blockquote>
  <p>both return an index of 0. </p>
</blockquote>

<p>0 is the correct answer here.</p>

<blockquote>
  <p>Am I missing something here?</p>
</blockquote>

<p>Not sure.</p>

<p>I can't reproduce your problem. I'm querying blocktrail like this:</p>

<pre><code>curl https://api.blocktrail.com/v1/tbtc/address/2N6qMqR9D4BTkD6fS1h6Sq3kRV2FeB1L14j/transactions?api_key=MY_APIKEY
</code></pre>

<p>and that returns all of the transactions for the address, none of which have an index of 4.</p>

<p>Can you post the line of code that calls their API?</p>
