Theranos blood test's Specificity and Accuracy?
Which patents are relevant for their device?


They currently only have about 27 issued patents (US) 
Of those patents about 10 of them are related to network/internet/health record/algorithm (so not really about their device)
The remaining patents focus on a few areas: sample acquisition (getting the blood drop and handling of it), Patch based technology (before they pivoted), sample quality analysis (this is key to making sure the small sample is good quality), microfluidics/modular device (these are the patents relating to the actual testing and device)


What are the limitations of multiplying so little blood?


From a molecular standpoint (PCR) the smaller sample you start with, the less of the original nucleic acid template you have to start with.  Lower end PCR testing uses 10uL of sample.  This is ok when you are trying to bring molecular diagnostics to the point of care or developing markets, but the best PCR tests use 50uL of sample (more than a drop of blood which is traditionally 25uL or so),  regardless of how good your device is, at some point you start amplifying junk. The better the primers and other reagents the less junk you amplify, but at the end of the day you want more sample to be more sensitive.
From a NON-molecular standpoint (chemistries, cellular analysis, coag, etc.), they aren't/can't multiply the analyte of interest.  In these tests, they rely more on dilution or small volumes to perform detection.  This is where their ability to reliably dilute and correct for the dilution comes into play. Although there is certain limits to this.  Coagulation tests would not be representative if you diluted the sample so in this case they will have to rely on working with a small volume.  Cellular analysis can only be diluted so much as you get to a point where you miss important but less common cell types.  Take eosinophils (a type of WBC) while they can get to 15 or 20 percent of all WBC cell types, in general they only make up a couple percent.  Assume that 2% of all your WBCs are eosinophils.  If you only have 3500 WBCs per 1uL of blood (which is on the lower end of normal), you have approximately only 70 of these cells in that same volume.  If you dilute the sample so that way there is more of it available for other tests like electrolytes, but you still analyze 1uL, The number of those cells is even less.  If you had perfect detection you might be ok, but you generally want to analyze more blood so that statistics work in your favor and your performance goes up. Most of the other chemistries, proteins, and as mentioned earlier, electrolytes will probably be ok for dilution and detection and in fact this is why there are plenty of small devices already out there that use a drop of blood and perform the same tests.
Their issue in diluting or amplifying analytes of interest is that biology still is governed by the laws of physics and even though technology may allow you to analyze samples down to 10nL, that just isn't use full in biology, and limits their their capability to perform the supposed menu of tests from one microtainer of blood.  They don't publicize that they may need to draw a venous sample (needle in your arm) for some tests and depending on what tests you order, you may need a separate finger prick for each test. 


How can Theranos blood test's be specific and accurate compared to conventional full blood test?


If they reliably control dilution of the small sample, they maybe able to provide high quality results for some tests.
Finger pricks actually can be easily skewed via technique.  Theranos has specially trained people to draw these samples, but it is time consuming >5 mins and until it is fully automated this is one variable that no matter how good sensors are, you can't correct for variation pre-analytically when you have that small sample.  Finger pricks also skew certain tests even when technique is good such as platelet and WBC values in the CBC.
I discussed the sample volume issue above regarding PCR amplification and how good tests use up to 50uL.  So if they compare to a 10uL test, they may be able to compete, but not full lab quality.  
A lot of the future techniques they have regarding small techniques (in their applications) like their coagulation tests work great in an academic setting, but they fail to be able to handle the full range of blood samples they will see, so it will be interesting to see how that plays out.


Takeaway


Theranos is working on modular micofluidic devices/cartridges that will use small sample
There are certain biological limitations that stand in the way of them performing all the tests in their catalog with only a drop of blood
The FDA will eventually be requiring them to submit their tests for approval as they are currently doing tests that are available on commercially and FDA approved devices already (this makes sense because LDTs were never ment to be used in place of standard tests and equipment and since there is NO published data on their performance it can be worrisome to providers and payer)
Their true business plan has yet to be elucidated, but if they really did have a box that did all this, they would be selling them to physicians and clincs where those results could actually be used in diagnosis rather than 4 hours later.
I hope they succeed, but there is just way too much hype to buy in on it yet.    


I am sorry I don't have sources, most of this is from intimate knowledge of the space and from the little info available on them so I could definitely be wrong on some of this.  I hope this helps!