Quintin John Lai
Vice President of Strategy and Investor Relations at West Pharmaceutical Services
Thank you, Eric, and good morning. Let's review the numbers in more detail. We'll first look at Q3 2023 revenues and profits, where we saw a mid-single-digit increase in organic net sales growth, an increase in diluted EPS and a decline in operating profit compared to the third quarter of 2022. I will also take you through the drivers impacting sales and margin in the quarter, as well as some balance sheet takeaways. And finally, we'll provide an update to our 2023 guidance. First up Q3. Our financial results are summarized on slide seven and a reconciliation of non-U.S. GAAP measures are described in slides 16 to 20. We reported net sales of $747.4 million, representing organic sales growth of 5.7%.
COVID-related net revenues are estimated to have been approximately $18 million in the quarter, a decline of $78 million compared to the same period last year. Looking at slide eight. Q3 proprietary products, organic net sales increased 3.2%. High-value products which made up approximately 76% of Proprietary Products segment sales grew by mid-single digits, led by customer demand for HPV components and devices. Taking a look at the performance of the market units, including the negative impact from a reduction of COVID-19-related sales, the generics market unit delivered high single-digit growth and the pharma market unit experienced low single-digit growth, both led by Westar components and Admin Systems.
The Biologics market unit also saw low single-digit growth driven by sales of Flurotec components and self-injection delivery devices. Our Contract Manufacturing segment experienced double-digit net sales, organic sales growth led by an increase in components and sales of components related to injection-related devices and health care diagnostic devices. Our adjusted operating profit margin of 24.2% was a 290 basis point decrease from the same period last year. Finally, adjusted diluted EPS increased 6.4% for Q3, excluding stock-based compensation, tax benefit, adjusted diluted EPS increased by 1% compared to last year. Now let's review the drivers in both our revenue and profit performance. On slide nine, we show the contribution to organic sales growth in the quarter.
Sales price increases contributed $46.2 million or 6.8 percentage points of growth in the quarter. Foreign currency tailwind was approximately $25.1 million or 3.7 percentage points of growth. Overall mix and volume negatively impacted sales by $7.3 million. This includes an approximate $78 million reduction in COVID-19-related net demand, partially offset by positive volume and mix contribution from our non-COVID base business. Looking at margin performance. Slide 10 shows our consolidated gross profit margin of 38.6% for Q3, down from 39.0% in the same period last year. Proprietary Products third quarter gross profit margin of 43.4% was 20 basis points lower than margin achieved in the same period last year.
The key driver for the decline in Proprietary Products gross profit margin was an unfavorable mix from a reduction in sales related to COVID-19 vaccines, offset by sales price increases that offset inflationary cost pressures in our plants. Contract Manufacturing, third quarter gross profit margin of 18.6% was 130 basis points higher than the margin achieved in the third quarter of last year, due to a favorable mix of products sold, and increased sale prices offset by inflationary pressures on our plant labor costs. Now let's look at our balance sheet and review how we've done in terms of generating cash for the business.
On slide 11, we have listed some key cash flow metrics. Operating cash flow was $537.4 million for the first nine months of 2023. An increase of $44.2 million compared to the same period last year, a 9% increase primarily due to improvement in working capital. Our third quarter 2023 year-to-date capital spending was $253.3 million, $63.6 million higher than the same period last year. We continue to leverage our capex to increase our high-value product manufacturing capacity. Working capital of approximately $1.44 billion at September 30, 2023, increased by $38.3 million from December 31, 2022, primarily due to growth in our current assets, offset by an increase in our current portion of long-term debt.
Our cash balance at September 30, 2023, was $898.6 million and was $4.3 million higher than our December 2022 balance. The small increase in cash is primarily driven by positive operating results, offset by increased repurchases under our share repurchase program and higher capex. Turning to guidance. Slide 12 provides a high-level summary. We're updating our full year 2023 net sales guidance and expect net sales to be in a range of $2.95 billion to $2.96 billion compared to a prior guidance range of $2.97 billion to $2.995 billion. There is an estimated full year 2023 tailwind of $20 million based on current FX rates, unchanged from prior guidance. We expect organic sales to be approximately 2% to 3% for the full year, compared to the prior guidance range of 3% to 4%.
We are raising our full year 2023 adjusted diluted EPS guidance to be in a range of $7.95 to $8 compared to a prior range of $7.65 to $7.80. Also, our capex guidance is $350 million for the year, unchanged from prior guidance. There are some key elements I want to bring to your attention. We have lowered our revenue guidance to reflect the recent trend with certain pharma and generic customers, slowing their restocking of inventory and increased inventory management as we head into the end of the year. We expect full year COVID-19 related sales to be approximately $68 million, compared to prior guide of $60 million. Net sales guidance also includes a reduction of $8 million, resulting from a divestiture of a European facility that produce standard Proprietary Products, and this is unchanged from prior guidance.
Full year 2023 adjusted diluted EPS range includes an FX tailwind of approximately $0.07, based on current FX exchange rates, compared to prior guidance of a tailwind of $0.05. The updated guidance also includes EPS of $0.41 associated with year-to-date 2023 tax benefits from stock base comp. Our guidance excludes future tax benefits from stock-based compensation. I would like to highlight that over the last five years, our base business growth, excluding COVID-19 has been within or above our construct of annual -- organic revenue growth of 7% to 9%. And over the same time period, we've averaged our annual operating margin expansion of over 100 basis points.
As Eric mentioned earlier, we are providing a preliminary look to 2024. Based on current trends in demand, we anticipate that West will again be within our long-range financial construct of organic sales growth and operating profit margin expansion. As usual, we'll provide more detailed guidance on 2024 in our February call.
I'd like to turn the call back over to Eric.