Laboratory testing for LA
Laboratory testing for LA
Laboratory testing for LA
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<strong>Laboratory</strong> <strong>testing</strong> <strong>for</strong> <strong>LA</strong>:<br />
‣ Two screening tests ‘negative’ in order to exclude <strong>LA</strong>;<br />
recommended*:<br />
‣ APTT (Activated Partial Thromboplastin Time) &<br />
‣ dRVVT (dilute Russell Viper Venom Time)<br />
‣ Either one ‘positive’ in order to identify <strong>LA</strong><br />
‣ Possible that no two labs use exactly the same <strong>LA</strong> procedure<br />
‣ APTT: reagents are <strong>LA</strong> ‘sensitive’ (variably) vs <strong>LA</strong> insensitive (variably)<br />
‣ dRVVT – some reagents are more sensitive to <strong>LA</strong> than others<br />
‣ APTT (mix vs no mix)<br />
‣ dRVVT (mix or no mix)<br />
‣ Mix (1:1 or other?)<br />
‣ Mix plasma (normal) used (commercial, in house, lyophilised, frozen)<br />
‣ Normal ranges – 20, 40 or more individuals? +/- 2SD, +/- 3 SD, >99 th percentile, etc?<br />
‣ Ratio, normalised ratio, % correction, Rosner index/ICA<br />
‣ Ratio – denominator = normal plasma value or median of reference interval (etc)<br />
‣ etc, etc<br />
* Pengo et al. JTH 2009;7:1737-40<br />
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