Facts are stubborn things but statistics are more pliable. For illustration of this old truism, look no further than the Scottish Government's reassuring statement regarding yesterday's mortality figures for hospital superbugs. The "downward trend" in deaths from the biggest killer, Clostridium Difficile (C Diff), showed that "new infection control measures were taking effect". Health Secretary Nicola Sturgeon suggested the figures "give cautious grounds for optimism". Last month the government claimed C Diff rates were at a "record low".

The stubborn facts are less reassuring. While the SNP administration's assertions are based on comparing figures for different three-month periods, the annual figures, released yesterday by the General Register Office for Scotland (GROS), reveal that, in 2008, 765 patients died after contracting C Diff, an annual increase of 28%. All but 54 died in hospital. In 248 cases, the bug was the main underlying cause of death, also a record figure and considerably more than swine flu. Thus the government's take on the statistics looks like a classic example of torturing the figures until they tell you what you want to hear.

An accompanying note from GROS suggests that the figures should be treated with caution as there may be discrepancies in how C Diff was recorded. Indeed. The Herald recently raised concerns about the death rate from C Diff at Gartnavel General Hospital in Glasgow, on the basis of figures supplied by Ms Sturgeon to Maryhill MSP Patricia Ferguson. Now a letter from the Health Secretary has revealed that the figures supplied contained a number of administrative errors, while admitting that 24 patients died at the hospital last year from C Diff, directly or indirectly. Ms Sturgeon's explanation, which would not be out of place in the Adventures of Alice in Wonderland, reinforces doubts about the integrity of the figures. In a case previously reported by The Herald, a death certificate was changed to include reference to C Diff only after the family complained. Britain's foremost bacteriologist, Professor Hugh Pennington, has said he believes C Diff should appear on death certificates more often than it does. If so, yesterday's figures are likely to be an underestimate. This is absolutely fundamental. If the impact of this infection is not being recorded consistently, how can the effectiveness of infection control measures be judged properly? With health boards and hospitals under pressure to meet targets for reducing hospital-acquired infections, do their figures give the full picture?

Yesterday's figures for both health board areas and individual hospitals are not reassuring. They do show real progress in the fight against MRSA, with deaths down nearly 15% on 2007, but falls in C Diff deaths at some hospitals are more than outweighed by rises elsewhere. Of particular concern are Borders General Hospital and Kirkcaldy's Victoria Infirmary, where eight people died directly from C Diff last year, and Aberdeen Royal Infirmary with 13 deaths, compared with two deaths each the year before.

Ms Sturgeon is certainly not complacent on this issue, as Labour had suggested yesterday. As someone who watched her own grandmother fight C Diff, before she died, she understands only too well the human tragedies behind these figures.

The government has committed £54m to tackling hospital infections but superbugs will not be beaten until we understand more about how outbreaks occur and which measures best contain them. The existing report into the outbreak at the Vale of Leven Hospital last year that killed 18 people did not drill deeply enough into the causes and circumstances. With C Diff continuing to claim lives from Shetland to the Borders, surely the time has now come to widen the promised public inquiry into that outbreak to take in the whole country?

Lord Coulsfield's decision to step down on health grounds clears the way to expand the remit and offer the chair to the person who is best qualified to understand this issue: Professor Hugh Pennington. Why has he not been asked?

Nobody wants to get C Diff. If you do, you will suffer terrible diarrhoea, searing pain and a high fever. If you are old and frail, you may die. Each death is a personal tragedy that could have been avoided. As the crusading journalist Paul Brodeur once observed: "Statistics are human beings with the tears wiped off."