Heart Care Info - Heart Disease Prevention & Treatment

Number needed to treat to harm (NNTH) analysis of impact of underlying cardiovascular factors on risk of abacavir-related heart attack

HTB South - Month, 2011 - i-base.info JD Kowalska from the D: A: D study presented a model looking at the 'number needed to treat to harm'(NNTH) in order to help interpret the clinical importance of the 90% increased relative risk (RR= 1.90), previously reported between abacavir use and the risk of heart ...

JD Kowalska from the D:A:D study presented a model looking at the ‘number needed to treat to harm’ (NNTH) in order to help interpret the clinical importance of the 90% increased relative risk (RR=1.90), previously reported between abacavir use and the risk of heart attack. [1, 2]

This estimate changed depending on an individuals underling cardiovascular risk. The underlying risk was calculated based on 5-year Framingham score [3] and the relative rate was assumed to remain constant across the range of underlying risk of MI.

The lowest NNTH values were observed in the high risk group, while the most dynamic changes in NNTH is in the low risk group, showing an exponential relationship between NNTH and underlying risk of MI. The NNTH dropped steeply from 185 with an underlying risk of MI of 0.6% to only 5 when underlying MI risk is 20%.

The importance of additional risk factors was illustrated by starting with a low risk patient (0.1% risk of MI); in this case, 1111 patients would need to be treated before seeing an abacavir-related MI. When two unfavourable risk components are present the NNTH drops to around 100 for most pairs, except smoking and low HDL, for which NNTH drops to 69. When all risk factors are unfavourable, in patients with 15% underlying CVD risk, only 7 people would need to be treated with abacavir to see a treatment associated MI. (See Table 1).