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Title: Lab Shift Plots: Baseline versus Maximum

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Title Lab Shift Plots: Baseline versus Maximum
Graph_Subgroup Labs Liver
Labs_Liver_Clinical_Question
Association: 1. What is the association between lab assessments? Are multiple lab values that are elevated or abnormal - either concurrently or not? ie how can we easily identify patients with simultaneous elevations in multiple lab tests over time?
Description This is a set of scatter plots displaying together the results of liver function tests (LFTs) in a clinical trial. Each panel shows the maximum upper limit of normal (ULN) value of a test over the treatment period plotted against the upper limit of normal for baseline. The lower x-axis represents the baseline ‘times upper limit of normal’ (xuln)for the parameters graphed where a value of 1 would mean that the result was normal. Any value above or below 1 would be considered above the upper limit of normal or below the upper limit of normal respectively. For instance, a value of 3 would be read as ‘3 times the upper limit of normal’. Upper limit of normal is calculated by dividing the standard result (CTSPedia dataset variable ‘lbstresn’) in numeric units by the standard high range limit (variable ‘lbstnrhi’). Original units can be substituted if needed as the upper limit of normal is normalized (has no units). The y-axis values are the on-study or post-baseline maximum xuln values. It is important to note that similar scale for the xuln axes (both x and y) should be maintained, making each panel a square. The plots are enhanced with horizontal reference lines to show levels of clinical concern. The macro within the code allows the end user to decide which version (2 panels x 2 panels or 1 panel x 4 panels) to create.


This is similar to the Lab Parameter Shift Plot in that it too is a scatter plot of lab parameters. However, this outputs either a 2x2 or 1x4 plot of baseline versus maximum ULN values while the lab Parameter Shift Plot outputs a 1x2 plot of baseline ULN versus all post-baseline ULN values.


One of the main interpretations of this graphic, in addition to determining if a patient is above a specific clinical level of concern, is to determine if a patient’s lab values have increased or decreased since baseline. The 45 degree reference line is included for ease of interpretation. An increase in lab parameter would be represented by any point above the 45 degree line. The farther the point moves toward the upper left quadrant, the larger the increase from baseline. Likewise, the farther the point moves below the reference line and towards the lower right quadrant, the large the decrease from baseline.
Contributor/Email Susan Duke (susan.p.duke@gsk.com)
Max Cherny (Max.2.Cherny@gsk.com)
Additional_Contributor_Info On behalf of authors, Peter Lane, Richard Heiberger, Mark K Jones & Sunil Mistry
Background

Keywords graphics, trellis, scatterplot, safety, LFT
References Amit, O, RM Heiberger, PW Lane, 2008. Graphical approaches to the analysis of safety data from clinical trials. Pharmaceut. Statist. 2008; 7: 20–35
Datasets CDISC Datasets
CDISC_Data ADLBC
Data_Format Gordon_format_data_table.png
CLASSIFICATIONS

Graph_Type Scatterplot
Variable_Relationship Continuous versus Continuous
Data_Types Continuous
Special_Considerations Because this graph uses one value for the x-axis (baseline value) and the maximum for the y-axis (on-study values), some caution is needed in interpretation. A slight upward drift from the diagonal is expected for purely analytic reasons.
Code_Available Yes
Software Program SAS, other
Software

R-Code - Attachment

R-Code

SAS-Code - Attachment Gordon - Lab Shift Plots - SAS Code
SAS-Code - v9.2 - Attachment Contributed by Sanjay Matange Matange - Lab Shift Plots - SAS Code v9.2
Click to enlarge image.
Stata-Code - Attachment

Stata-Code

Other Code - Attachment S-Plus Code: Gordon - Lab Shift Plots - S-Plus Code
Other Code

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Reference Image Cherny_t2t_200.png
Topic revision: r18 - 01 May 2013 - 18:08:36 - MaryBanach
 

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