Description Usage Arguments Details Value Author(s) References See Also

Compute sensitivity and specificity

1 |

`X` |
n by S matrix of longitudinal score/biomarker for i-th subject at j-th occasion (NA if unmeasured) |

`etime` |
n vector with follow-up times |

`status` |
n vector with event indicators |

`u` |
Lower limit for evaluation of sensitivity and
specificity. Defaults to |

`tt` |
Upper limit (time-horizon) for evaluation of sensitivity and specificity. |

`s` |
Scalar number of measurements/visits to use for each subject. s<=S |

`vtimes` |
S vector with visit times |

`cutoff` |
cutoff for definining events. Defaults to |

`fc` |
Events are defined as fc = 1. Defaults to $I(cup X(t_j)>cutoff)$ |

Sensitivity and specificities for a time-dependent multiply-measured marker are defined as

Se(t,c,s,u) = Pr(f_c(X(t_1),X(t_2),...,X(t_s_i))| u <= T <= t),

and

Sp(t,c,s,u) = 1-Pr(f_c(X(t_1),X(t_2),...,X(t_s_i)) | T > t)

for some fixed f_c, where c is a cutoff. The default for f_c is that a positive diagnosis is given as soon as any measurement among the s considered is above the threshold.

A vector with the following elements:

`sens` | Sensitivity at the cutoff |

`spec` | Specificity at the cutoff |

Alessio Farcomeni alessio.farcomeni@uniroma1.it

Barbati, G. and Farcomeni, A. (2017) Prognostic assessment of
repeatedly measured time-dependent biomarkers, with application to
dilated cardiomuopathy, *Statistical Methods \& Applications*, in
press

roc, auc, butstrap, maxauc

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