Simple query_posts not working

Hi There, can anyone help me understand as to why this isn’t working? It seems simple enough and is what the codex suggests but it has no affect on what categories show – Much appreciated

<?php query_posts($query_string . "&cat=-1"); ?>
			<?php if ( have_posts() ) : ?>
				<?php while ( have_posts() ) : the_post(); ?>
					<?php
						get_template_part( 'content', get_post_format() );
					?>

				<?php endwhile; ?>

				<?php matt_content_nav( 'nav-below' ); ?>

			<?php else : ?>
				<?php get_template_part( 'no-results', 'index' ); ?>
			<?php endif; ?>